diff --git a/include/v8.h b/include/v8.h
index b2ae4cb3fa..340baa74ab 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -1380,12 +1380,11 @@ class V8_EXPORT ScriptCompiler {
     virtual void ResetToBookmark();
   };
 
-
   /**
    * Source code which can be streamed into V8 in pieces. It will be parsed
-   * while streaming. It can be compiled after the streaming is complete.
-   * StreamedSource must be kept alive while the streaming task is ran (see
-   * ScriptStreamingTask below).
+   * while streaming and compiled after parsing has completed. StreamedSource
+   * must be kept alive while the streaming task is run (see ScriptStreamingTask
+   * below).
    */
   class V8_EXPORT StreamedSource {
    public:
@@ -1394,29 +1393,35 @@ class V8_EXPORT ScriptCompiler {
     StreamedSource(ExternalSourceStream* source_stream, Encoding encoding);
     ~StreamedSource();
 
-    // Ownership of the CachedData or its buffers is *not* transferred to the
-    // caller. The CachedData object is alive as long as the StreamedSource
-    // object is alive.
-    const CachedData* GetCachedData() const;
+    V8_DEPRECATED("No longer used", const CachedData* GetCachedData() const) {
+      return nullptr;
+    }
 
-    internal::ScriptStreamingData* impl() const { return impl_; }
+    internal::ScriptStreamingData* impl() const { return impl_.get(); }
 
     // Prevent copying.
     StreamedSource(const StreamedSource&) = delete;
     StreamedSource& operator=(const StreamedSource&) = delete;
 
    private:
-    internal::ScriptStreamingData* impl_;
+    std::unique_ptr<internal::ScriptStreamingData> impl_;
   };
 
   /**
    * A streaming task which the embedder must run on a background thread to
    * stream scripts into V8. Returned by ScriptCompiler::StartStreamingScript.
    */
-  class ScriptStreamingTask {
+  class V8_EXPORT ScriptStreamingTask final {
    public:
-    virtual ~ScriptStreamingTask() = default;
-    virtual void Run() = 0;
+    void Run();
+
+   private:
+    friend class ScriptCompiler;
+
+    explicit ScriptStreamingTask(internal::ScriptStreamingData* data)
+        : data_(data) {}
+
+    internal::ScriptStreamingData* data_;
   };
 
   enum CompileOptions {
diff --git a/src/api.cc b/src/api.cc
index c41e86be76..3c9e0aaf84 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -59,6 +59,7 @@
 #include "src/objects/module-inl.h"
 #include "src/objects/ordered-hash-table-inl.h"
 #include "src/objects/templates.h"
+#include "src/parsing/parse-info.h"
 #include "src/parsing/parser.h"
 #include "src/parsing/scanner-character-streams.h"
 #include "src/pending-compilation-error-handler.h"
@@ -2009,24 +2010,15 @@ ScriptCompiler::CachedData::~CachedData() {
   }
 }
 
-
 bool ScriptCompiler::ExternalSourceStream::SetBookmark() { return false; }
 
-
 void ScriptCompiler::ExternalSourceStream::ResetToBookmark() { UNREACHABLE(); }
 
 ScriptCompiler::StreamedSource::StreamedSource(ExternalSourceStream* stream,
                                                Encoding encoding)
     : impl_(new i::ScriptStreamingData(stream, encoding)) {}
 
-ScriptCompiler::StreamedSource::~StreamedSource() { delete impl_; }
-
-
-const ScriptCompiler::CachedData*
-ScriptCompiler::StreamedSource::GetCachedData() const {
-  return impl_->cached_data.get();
-}
-
+ScriptCompiler::StreamedSource::~StreamedSource() = default;
 
 Local<Script> UnboundScript::BindToCurrentContext() {
   auto function_info =
@@ -2038,7 +2030,6 @@ Local<Script> UnboundScript::BindToCurrentContext() {
   return ToApiHandle<Script>(function);
 }
 
-
 int UnboundScript::GetId() {
   auto function_info =
       i::Handle<i::SharedFunctionInfo>::cast(Utils::OpenHandle(this));
@@ -2534,6 +2525,7 @@ MaybeLocal<Function> ScriptCompiler::CompileFunctionInContext(
   RETURN_ESCAPED(Utils::CallableToLocal(result));
 }
 
+void ScriptCompiler::ScriptStreamingTask::Run() { data_->task->Run(); }
 
 ScriptCompiler::ScriptStreamingTask* ScriptCompiler::StartStreamingScript(
     Isolate* v8_isolate, StreamedSource* source, CompileOptions options) {
@@ -2544,10 +2536,13 @@ ScriptCompiler::ScriptStreamingTask* ScriptCompiler::StartStreamingScript(
   // TODO(rmcilroy): remove CompileOptions from the API.
   CHECK(options == ScriptCompiler::kNoCompileOptions);
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(v8_isolate);
-  return i::Compiler::NewBackgroundCompileTask(source->impl(), isolate);
+  i::ScriptStreamingData* data = source->impl();
+  std::unique_ptr<i::BackgroundCompileTask> task =
+      base::make_unique<i::BackgroundCompileTask>(data, isolate);
+  data->task = std::move(task);
+  return new ScriptCompiler::ScriptStreamingTask(data);
 }
 
-
 MaybeLocal<Script> ScriptCompiler::Compile(Local<Context> context,
                                            StreamedSource* v8_source,
                                            Local<String> full_source_string,
@@ -2562,11 +2557,11 @@ MaybeLocal<Script> ScriptCompiler::Compile(Local<Context> context,
       isolate, origin.ResourceName(), origin.ResourceLineOffset(),
       origin.ResourceColumnOffset(), origin.SourceMapUrl(),
       origin.HostDefinedOptions());
-  i::ScriptStreamingData* streaming_data = v8_source->impl();
+  i::ScriptStreamingData* data = v8_source->impl();
 
   i::MaybeHandle<i::SharedFunctionInfo> maybe_function_info =
       i::Compiler::GetSharedFunctionInfoForStreamedScript(
-          isolate, str, script_details, origin.Options(), streaming_data);
+          isolate, str, script_details, origin.Options(), data);
 
   i::Handle<i::SharedFunctionInfo> result;
   has_pending_exception = !maybe_function_info.ToHandle(&result);
diff --git a/src/compiler.cc b/src/compiler.cc
index fba79c4f46..a30d186ee1 100644
--- a/src/compiler.cc
+++ b/src/compiler.cc
@@ -941,93 +941,75 @@ std::unique_ptr<UnoptimizedCompilationJob> CompileTopLevelOnBackgroundThread(
   return outer_function_job;
 }
 
-class BackgroundCompileTask : public ScriptCompiler::ScriptStreamingTask {
- public:
-  BackgroundCompileTask(ScriptStreamingData* source, Isolate* isolate);
+}  // namespace
 
-  void Run() override;
-
- private:
-  ScriptStreamingData* source_;  // Not owned.
-  int stack_size_;
-  WorkerThreadRuntimeCallStats* worker_thread_runtime_call_stats_;
-  AccountingAllocator* allocator_;
-  TimedHistogram* timer_;
-
-  DISALLOW_COPY_AND_ASSIGN(BackgroundCompileTask);
-};
-
-BackgroundCompileTask::BackgroundCompileTask(ScriptStreamingData* source,
+BackgroundCompileTask::BackgroundCompileTask(ScriptStreamingData* streamed_data,
                                              Isolate* isolate)
-    : source_(source),
+    : info_(new ParseInfo(isolate)),
       stack_size_(i::FLAG_stack_size),
       worker_thread_runtime_call_stats_(
           isolate->counters()->worker_thread_runtime_call_stats()),
+      allocator_(isolate->allocator()),
       timer_(isolate->counters()->compile_script_on_background()) {
   VMState<PARSER> state(isolate);
 
   // Prepare the data for the internalization phase and compilation phase, which
   // will happen in the main thread after parsing.
-  ParseInfo* info = new ParseInfo(isolate);
   LOG(isolate, ScriptEvent(Logger::ScriptEventType::kStreamingCompile,
-                           info->script_id()));
-  info->set_toplevel();
-  info->set_unicode_cache(&source_->unicode_cache);
-  info->set_allow_lazy_parsing();
-  if (V8_UNLIKELY(info->block_coverage_enabled())) {
-    info->AllocateSourceRangeMap();
+                           info_->script_id()));
+  info_->set_toplevel();
+  info_->set_unicode_cache(&unicode_cache_);
+  info_->set_allow_lazy_parsing();
+  if (V8_UNLIKELY(info_->block_coverage_enabled())) {
+    info_->AllocateSourceRangeMap();
   }
   LanguageMode language_mode = construct_language_mode(FLAG_use_strict);
-  info->set_language_mode(
-      stricter_language_mode(info->language_mode(), language_mode));
+  info_->set_language_mode(
+      stricter_language_mode(info_->language_mode(), language_mode));
 
-  source->info.reset(info);
-  allocator_ = isolate->allocator();
+  std::unique_ptr<Utf16CharacterStream> stream(ScannerStream::For(
+      streamed_data->source_stream.get(), streamed_data->encoding));
+  info_->set_character_stream(std::move(stream));
 }
 
 void BackgroundCompileTask::Run() {
   TimedHistogramScope timer(timer_);
   DisallowHeapAccess no_heap_access;
 
-  source_->info->set_on_background_thread(true);
+  info_->set_on_background_thread(true);
 
   // Get a runtime call stats table associated with the current worker thread.
   WorkerThreadRuntimeCallStatsScope runtime_call_stats_scope(
       worker_thread_runtime_call_stats_);
-  RuntimeCallStats* old_runtime_call_stats =
-      source_->info->runtime_call_stats();
-  source_->info->set_runtime_call_stats(runtime_call_stats_scope.Get());
+  RuntimeCallStats* old_runtime_call_stats = info_->runtime_call_stats();
+  info_->set_runtime_call_stats(runtime_call_stats_scope.Get());
+  info_->character_stream()->set_runtime_call_stats(
+      runtime_call_stats_scope.Get());
 
   // Reset the stack limit of the parser to reflect correctly that we're on a
   // background thread.
-  uintptr_t old_stack_limit = source_->info->stack_limit();
+  uintptr_t old_stack_limit = info_->stack_limit();
   uintptr_t stack_limit = GetCurrentStackPosition() - stack_size_ * KB;
-  source_->info->set_stack_limit(stack_limit);
-
-  std::unique_ptr<Utf16CharacterStream> stream(
-      ScannerStream::For(source_->source_stream.get(), source_->encoding,
-                         source_->info->runtime_call_stats()));
-  source_->info->set_character_stream(std::move(stream));
+  info_->set_stack_limit(stack_limit);
 
   // Parser needs to stay alive for finalizing the parsing on the main
   // thread.
-  source_->parser.reset(new Parser(source_->info.get()));
-  source_->parser->set_stack_limit(stack_limit);
-  source_->parser->InitializeEmptyScopeChain(source_->info.get());
+  parser_.reset(new Parser(info_.get()));
+  parser_->set_stack_limit(stack_limit);
+  parser_->InitializeEmptyScopeChain(info_.get());
 
-  source_->parser->ParseOnBackground(source_->info.get());
-  if (source_->info->literal() != nullptr) {
+  parser_->ParseOnBackground(info_.get());
+  if (info_->literal() != nullptr) {
     // Parsing has succeeded, compile.
-    source_->outer_function_job = CompileTopLevelOnBackgroundThread(
-        source_->info.get(), allocator_, &source_->inner_function_jobs);
+    outer_function_job_ = CompileTopLevelOnBackgroundThread(
+        info_.get(), allocator_, &inner_function_jobs_);
   }
 
-  source_->info->set_stack_limit(old_stack_limit);
-  source_->info->set_runtime_call_stats(old_runtime_call_stats);
-  source_->info->set_on_background_thread(false);
+  info_->set_stack_limit(old_stack_limit);
+  info_->set_runtime_call_stats(old_runtime_call_stats);
+  info_->set_on_background_thread(false);
 }
 
-}  // namespace
 
 // ----------------------------------------------------------------------------
 // Implementation of Compiler
@@ -1761,11 +1743,6 @@ MaybeHandle<JSFunction> Compiler::GetWrappedFunction(
                                                             NOT_TENURED);
 }
 
-ScriptCompiler::ScriptStreamingTask* Compiler::NewBackgroundCompileTask(
-    ScriptStreamingData* source, Isolate* isolate) {
-  return new BackgroundCompileTask(source, isolate);
-}
-
 MaybeHandle<SharedFunctionInfo>
 Compiler::GetSharedFunctionInfoForStreamedScript(
     Isolate* isolate, Handle<String> source,
@@ -1779,7 +1756,9 @@ Compiler::GetSharedFunctionInfoForStreamedScript(
   isolate->counters()->total_load_size()->Increment(source_length);
   isolate->counters()->total_compile_size()->Increment(source_length);
 
-  ParseInfo* parse_info = streaming_data->info.get();
+  BackgroundCompileTask* task = streaming_data->task.get();
+  ParseInfo* parse_info = task->info();
+  DCHECK(parse_info->is_toplevel());
   // Check if compile cache already holds the SFI, if so no need to finalize
   // the code compiled on the background thread.
   CompilationCache* compilation_cache = isolate->compilation_cache();
@@ -1798,8 +1777,8 @@ Compiler::GetSharedFunctionInfoForStreamedScript(
     Handle<Script> script =
         NewScript(isolate, parse_info, source, script_details, origin_options,
                   NOT_NATIVES_CODE);
-    streaming_data->parser->UpdateStatistics(isolate, script);
-    streaming_data->parser->HandleSourceURLComments(isolate, script);
+    task->parser()->UpdateStatistics(isolate, script);
+    task->parser()->HandleSourceURLComments(isolate, script);
 
     if (parse_info->literal() == nullptr) {
       // Parsing has failed - report error messages.
@@ -1807,10 +1786,10 @@ Compiler::GetSharedFunctionInfoForStreamedScript(
           isolate, script, parse_info->ast_value_factory());
     } else {
       // Parsing has succeeded - finalize compilation.
-      if (streaming_data->outer_function_job) {
-        maybe_result = FinalizeTopLevel(
-            parse_info, isolate, streaming_data->outer_function_job.get(),
-            &streaming_data->inner_function_jobs);
+      if (task->outer_function_job()) {
+        maybe_result =
+            FinalizeTopLevel(parse_info, isolate, task->outer_function_job(),
+                             task->inner_function_jobs());
       } else {
         // Compilation failed on background thread - throw an exception.
         FailWithPendingException(isolate, parse_info,
@@ -1927,12 +1906,7 @@ ScriptStreamingData::ScriptStreamingData(
 
 ScriptStreamingData::~ScriptStreamingData() = default;
 
-void ScriptStreamingData::Release() {
-  parser.reset();
-  info.reset();
-  outer_function_job.reset();
-  inner_function_jobs.clear();
-}
+void ScriptStreamingData::Release() { task.reset(); }
 
 }  // namespace internal
 }  // namespace v8
diff --git a/src/compiler.h b/src/compiler.h
index 359f6962e7..801c6cc686 100644
--- a/src/compiler.h
+++ b/src/compiler.h
@@ -20,6 +20,7 @@ namespace v8 {
 namespace internal {
 
 // Forward declarations.
+class BackgroundCompileTask;
 class JavaScriptFrame;
 class OptimizedCompilationInfo;
 class OptimizedCompilationJob;
@@ -27,8 +28,10 @@ class ParseInfo;
 class Parser;
 class ScriptData;
 struct ScriptStreamingData;
+class TimedHistogram;
 class UnoptimizedCompilationInfo;
 class UnoptimizedCompilationJob;
+class WorkerThreadRuntimeCallStats;
 
 typedef std::forward_list<std::unique_ptr<UnoptimizedCompilationJob>>
     UnoptimizedCompilationJobList;
@@ -61,13 +64,6 @@ class V8_EXPORT_PRIVATE Compiler : public AllStatic {
   V8_WARN_UNUSED_RESULT static MaybeHandle<SharedFunctionInfo>
   CompileForLiveEdit(ParseInfo* parse_info, Isolate* isolate);
 
-  // Creates a new task that when run will parse and compile the streamed
-  // script associated with |streaming_data| and can be finalized with
-  // Compiler::GetSharedFunctionInfoForStreamedScript.
-  // Note: does not take ownership of streaming_data.
-  static ScriptCompiler::ScriptStreamingTask* NewBackgroundCompileTask(
-      ScriptStreamingData* streaming_data, Isolate* isolate);
-
   // Generate and install code from previously queued compilation job.
   static bool FinalizeCompilationJob(UnoptimizedCompilationJob* job,
                                      Handle<SharedFunctionInfo> shared_info,
@@ -317,6 +313,47 @@ class OptimizedCompilationJob : public CompilationJob {
   const char* compiler_name_;
 };
 
+class BackgroundCompileTask {
+ public:
+  // Creates a new task that when run will parse and compile the streamed
+  // script associated with |data| and can be finalized with
+  // Compiler::GetSharedFunctionInfoForStreamedScript.
+  // Note: does not take ownership of |data|.
+  BackgroundCompileTask(ScriptStreamingData* data, Isolate* isolate);
+
+  void Run();
+
+  ParseInfo* info() { return info_.get(); }
+  Parser* parser() { return parser_.get(); }
+  UnoptimizedCompilationJob* outer_function_job() {
+    return outer_function_job_.get();
+  }
+  UnoptimizedCompilationJobList* inner_function_jobs() {
+    return &inner_function_jobs_;
+  }
+
+ private:
+  // Data needed for parsing, and data needed to to be passed between thread
+  // between parsing and compilation. These need to be initialized before the
+  // compilation starts.
+  std::unique_ptr<ParseInfo> info_;
+  std::unique_ptr<Parser> parser_;
+  // TODO(rmcilroy): Consider having thread-local unicode-caches rather than
+  // creating a new one each time.
+  UnicodeCache unicode_cache_;
+
+  // Data needed for finalizing compilation after background compilation.
+  std::unique_ptr<UnoptimizedCompilationJob> outer_function_job_;
+  UnoptimizedCompilationJobList inner_function_jobs_;
+
+  int stack_size_;
+  WorkerThreadRuntimeCallStats* worker_thread_runtime_call_stats_;
+  AccountingAllocator* allocator_;
+  TimedHistogram* timer_;
+
+  DISALLOW_COPY_AND_ASSIGN(BackgroundCompileTask);
+};
+
 // Contains all data which needs to be transmitted between threads for
 // background parsing and compiling and finalizing it on the main thread.
 struct ScriptStreamingData {
@@ -329,18 +366,9 @@ struct ScriptStreamingData {
   // Internal implementation of v8::ScriptCompiler::StreamedSource.
   std::unique_ptr<ScriptCompiler::ExternalSourceStream> source_stream;
   ScriptCompiler::StreamedSource::Encoding encoding;
-  std::unique_ptr<ScriptCompiler::CachedData> cached_data;
 
-  // Data needed for parsing, and data needed to to be passed between thread
-  // between parsing and compilation. These need to be initialized before the
-  // compilation starts.
-  UnicodeCache unicode_cache;
-  std::unique_ptr<ParseInfo> info;
-  std::unique_ptr<Parser> parser;
-
-  // Data needed for finalizing compilation after background compilation.
-  std::unique_ptr<UnoptimizedCompilationJob> outer_function_job;
-  UnoptimizedCompilationJobList inner_function_jobs;
+  // Task that performs background parsing and compilation.
+  std::unique_ptr<BackgroundCompileTask> task;
 
   DISALLOW_COPY_AND_ASSIGN(ScriptStreamingData);
 };
diff --git a/src/parsing/scanner-character-streams.cc b/src/parsing/scanner-character-streams.cc
index 717ad925a8..8472e9f4fc 100644
--- a/src/parsing/scanner-character-streams.cc
+++ b/src/parsing/scanner-character-streams.cc
@@ -88,7 +88,7 @@ class OnHeapStream {
     UNREACHABLE();
   }
 
-  Range<Char> GetDataAt(size_t pos) {
+  Range<Char> GetDataAt(size_t pos, RuntimeCallStats* stats) {
     return {&string_->GetChars()[start_offset_ + Min(length_, pos)],
             &string_->GetChars()[start_offset_ + length_]};
   }
@@ -118,7 +118,7 @@ class ExternalStringStream {
   ExternalStringStream(const ExternalStringStream& other)
       : lock_(other.lock_), data_(other.data_), length_(other.length_) {}
 
-  Range<Char> GetDataAt(size_t pos) {
+  Range<Char> GetDataAt(size_t pos, RuntimeCallStats* stats) {
     return {&data_[Min(length_, pos)], &data_[length_]};
   }
 
@@ -137,7 +137,7 @@ class TestingStream {
  public:
   TestingStream(const Char* data, size_t length)
       : data_(data), length_(length) {}
-  Range<Char> GetDataAt(size_t pos) {
+  Range<Char> GetDataAt(size_t pos, RuntimeCallStats* stats) {
     return {&data_[Min(length_, pos)], &data_[length_]};
   }
 
@@ -153,17 +153,16 @@ class TestingStream {
 template <typename Char>
 class ChunkedStream {
  public:
-  ChunkedStream(ScriptCompiler::ExternalSourceStream* source,
-                RuntimeCallStats* stats)
-      : source_(source), stats_(stats) {}
+  explicit ChunkedStream(ScriptCompiler::ExternalSourceStream* source)
+      : source_(source) {}
 
   ChunkedStream(const ChunkedStream& other) {
     // TODO(rmcilroy): Implement cloning for chunked streams.
     UNREACHABLE();
   }
 
-  Range<Char> GetDataAt(size_t pos) {
-    Chunk chunk = FindChunk(pos);
+  Range<Char> GetDataAt(size_t pos, RuntimeCallStats* stats) {
+    Chunk chunk = FindChunk(pos, stats);
     size_t buffer_end = chunk.length;
     size_t buffer_pos = Min(buffer_end, pos - chunk.position);
     return {&chunk.data[buffer_pos], &chunk.data[buffer_end]};
@@ -187,13 +186,13 @@ class ChunkedStream {
     size_t end_position() const { return position + length; }
   };
 
-  Chunk FindChunk(size_t position) {
-    while (V8_UNLIKELY(chunks_.empty())) FetchChunk(size_t{0});
+  Chunk FindChunk(size_t position, RuntimeCallStats* stats) {
+    while (V8_UNLIKELY(chunks_.empty())) FetchChunk(size_t{0}, stats);
 
     // Walk forwards while the position is in front of the current chunk.
     while (position >= chunks_.back().end_position() &&
            chunks_.back().length > 0) {
-      FetchChunk(chunks_.back().end_position());
+      FetchChunk(chunks_.back().end_position(), stats);
     }
 
     // Walk backwards.
@@ -213,11 +212,11 @@ class ChunkedStream {
                          length / sizeof(Char));
   }
 
-  void FetchChunk(size_t position) {
+  void FetchChunk(size_t position, RuntimeCallStats* stats) {
     const uint8_t* data = nullptr;
     size_t length;
     {
-      RuntimeCallTimerScope scope(stats_,
+      RuntimeCallTimerScope scope(stats,
                                   RuntimeCallCounterId::kGetMoreDataCallback);
       length = source_->GetMoreData(&data);
     }
@@ -225,102 +224,11 @@ class ChunkedStream {
   }
 
   ScriptCompiler::ExternalSourceStream* source_;
-  RuntimeCallStats* stats_;
 
  protected:
   std::vector<struct Chunk> chunks_;
 };
 
-template <typename Char>
-class Utf8ChunkedStream : public ChunkedStream<uint16_t> {
- public:
-  Utf8ChunkedStream(ScriptCompiler::ExternalSourceStream* source,
-                    RuntimeCallStats* stats)
-      : ChunkedStream<uint16_t>(source, stats) {}
-
-  STATIC_ASSERT(sizeof(Char) == sizeof(uint16_t));
-  void ProcessChunk(const uint8_t* data, size_t position, size_t length) final {
-    if (length == 0) {
-      unibrow::uchar t = unibrow::Utf8::ValueOfIncrementalFinish(&state_);
-      if (t != unibrow::Utf8::kBufferEmpty) {
-        DCHECK_EQ(t, unibrow::Utf8::kBadChar);
-        incomplete_char_ = 0;
-        uint16_t* result = new uint16_t[1];
-        result[0] = unibrow::Utf8::kBadChar;
-        chunks_.emplace_back(result, position, 1);
-        position++;
-      }
-      chunks_.emplace_back(nullptr, position, 0);
-      delete[] data;
-      return;
-    }
-
-    // First count the number of complete characters that can be produced.
-
-    unibrow::Utf8::State state = state_;
-    uint32_t incomplete_char = incomplete_char_;
-    bool seen_bom = seen_bom_;
-
-    size_t i = 0;
-    size_t chars = 0;
-    while (i < length) {
-      unibrow::uchar t = unibrow::Utf8::ValueOfIncremental(data[i], &i, &state,
-                                                           &incomplete_char);
-      if (!seen_bom && t == kUtf8Bom && position + chars == 0) {
-        seen_bom = true;
-        // BOM detected at beginning of the stream. Don't copy it.
-      } else if (t != unibrow::Utf8::kIncomplete) {
-        chars++;
-        if (t > unibrow::Utf16::kMaxNonSurrogateCharCode) chars++;
-      }
-    }
-
-    // Process the data.
-
-    // If there aren't any complete characters, update the state without
-    // producing a chunk.
-    if (chars == 0) {
-      state_ = state;
-      incomplete_char_ = incomplete_char;
-      seen_bom_ = seen_bom;
-      delete[] data;
-      return;
-    }
-
-    // Update the state and produce a chunk with complete characters.
-    uint16_t* result = new uint16_t[chars];
-    uint16_t* cursor = result;
-    i = 0;
-
-    while (i < length) {
-      unibrow::uchar t = unibrow::Utf8::ValueOfIncremental(data[i], &i, &state_,
-                                                           &incomplete_char_);
-      if (V8_LIKELY(t < kUtf8Bom)) {
-        *(cursor++) = static_cast<uc16>(t);  // The by most frequent case.
-      } else if (t == unibrow::Utf8::kIncomplete) {
-        continue;
-      } else if (!seen_bom_ && t == kUtf8Bom && position == 0 &&
-                 cursor == result) {
-        // BOM detected at beginning of the stream. Don't copy it.
-        seen_bom_ = true;
-      } else if (t <= unibrow::Utf16::kMaxNonSurrogateCharCode) {
-        *(cursor++) = static_cast<uc16>(t);
-      } else {
-        *(cursor++) = unibrow::Utf16::LeadSurrogate(t);
-        *(cursor++) = unibrow::Utf16::TrailSurrogate(t);
-      }
-    }
-
-    chunks_.emplace_back(result, position, chars);
-    delete[] data;
-  }
-
- private:
-  uint32_t incomplete_char_ = 0;
-  unibrow::Utf8::State state_ = unibrow::Utf8::State::kAccept;
-  bool seen_bom_ = false;
-};
-
 // Provides a buffered utf-16 view on the bytes from the underlying ByteStream.
 // Chars are buffered if either the underlying stream isn't utf-16 or the
 // underlying utf-16 stream might move (is on-heap).
@@ -349,7 +257,8 @@ class BufferedCharacterStream : public Utf16CharacterStream {
     buffer_start_ = &buffer_[0];
     buffer_cursor_ = buffer_start_;
 
-    Range<uint8_t> range = byte_stream_.GetDataAt(position);
+    Range<uint8_t> range =
+        byte_stream_.GetDataAt(position, runtime_call_stats());
     if (range.length() == 0) {
       buffer_end_ = buffer_start_;
       return false;
@@ -401,7 +310,8 @@ class UnbufferedCharacterStream : public Utf16CharacterStream {
   bool ReadBlock() final {
     size_t position = pos();
     buffer_pos_ = position;
-    Range<uint16_t> range = byte_stream_.GetDataAt(position);
+    Range<uint16_t> range =
+        byte_stream_.GetDataAt(position, runtime_call_stats());
     buffer_start_ = range.start;
     buffer_end_ = range.end;
     buffer_cursor_ = buffer_start_;
@@ -446,7 +356,7 @@ class RelocatingCharacterStream
   }
 
   void UpdateBufferPointers() {
-    Range<uint16_t> range = byte_stream_.GetDataAt(0);
+    Range<uint16_t> range = byte_stream_.GetDataAt(0, runtime_call_stats());
     if (range.start != buffer_start_) {
       buffer_cursor_ = (buffer_cursor_ - buffer_start_) + range.start;
       buffer_start_ = range.start;
@@ -512,11 +422,9 @@ bool BufferedUtf16CharacterStream::ReadBlock() {
 class Utf8ExternalStreamingStream : public BufferedUtf16CharacterStream {
  public:
   Utf8ExternalStreamingStream(
-      ScriptCompiler::ExternalSourceStream* source_stream,
-      RuntimeCallStats* stats)
+      ScriptCompiler::ExternalSourceStream* source_stream)
       : current_({0, {0, 0, 0, unibrow::Utf8::State::kAccept}}),
-        source_stream_(source_stream),
-        stats_(stats) {}
+        source_stream_(source_stream) {}
   ~Utf8ExternalStreamingStream() final {
     for (size_t i = 0; i < chunks_.size(); i++) delete[] chunks_[i].data;
   }
@@ -574,7 +482,6 @@ class Utf8ExternalStreamingStream : public BufferedUtf16CharacterStream {
   std::vector<Chunk> chunks_;
   Position current_;
   ScriptCompiler::ExternalSourceStream* source_stream_;
-  RuntimeCallStats* stats_;
 };
 
 bool Utf8ExternalStreamingStream::SkipToPosition(size_t position) {
@@ -668,7 +575,7 @@ void Utf8ExternalStreamingStream::FillBufferFromCurrentChunk() {
 }
 
 bool Utf8ExternalStreamingStream::FetchChunk() {
-  RuntimeCallTimerScope scope(stats_,
+  RuntimeCallTimerScope scope(runtime_call_stats(),
                               RuntimeCallCounterId::kGetMoreDataCallback);
   DCHECK_EQ(current_.chunk_no, chunks_.size());
   DCHECK(chunks_.empty() || chunks_.back().length != 0);
@@ -845,17 +752,16 @@ std::unique_ptr<Utf16CharacterStream> ScannerStream::ForTesting(
 
 Utf16CharacterStream* ScannerStream::For(
     ScriptCompiler::ExternalSourceStream* source_stream,
-    v8::ScriptCompiler::StreamedSource::Encoding encoding,
-    RuntimeCallStats* stats) {
+    v8::ScriptCompiler::StreamedSource::Encoding encoding) {
   switch (encoding) {
     case v8::ScriptCompiler::StreamedSource::TWO_BYTE:
       return new UnbufferedCharacterStream<ChunkedStream>(
-          static_cast<size_t>(0), source_stream, stats);
+          static_cast<size_t>(0), source_stream);
     case v8::ScriptCompiler::StreamedSource::ONE_BYTE:
       return new BufferedCharacterStream<ChunkedStream>(static_cast<size_t>(0),
-                                                        source_stream, stats);
+                                                        source_stream);
     case v8::ScriptCompiler::StreamedSource::UTF8:
-      return new Utf8ExternalStreamingStream(source_stream, stats);
+      return new Utf8ExternalStreamingStream(source_stream);
   }
   UNREACHABLE();
 }
diff --git a/src/parsing/scanner-character-streams.h b/src/parsing/scanner-character-streams.h
index 091ef5b8ea..4c85f5383f 100644
--- a/src/parsing/scanner-character-streams.h
+++ b/src/parsing/scanner-character-streams.h
@@ -24,8 +24,7 @@ class V8_EXPORT_PRIVATE ScannerStream {
                                    int start_pos, int end_pos);
   static Utf16CharacterStream* For(
       ScriptCompiler::ExternalSourceStream* source_stream,
-      ScriptCompiler::StreamedSource::Encoding encoding,
-      RuntimeCallStats* stats);
+      ScriptCompiler::StreamedSource::Encoding encoding);
 
   static std::unique_ptr<Utf16CharacterStream> ForTesting(const char* data);
   static std::unique_ptr<Utf16CharacterStream> ForTesting(const char* data,
diff --git a/src/parsing/scanner.h b/src/parsing/scanner.h
index 22202810cf..4cbf1999f5 100644
--- a/src/parsing/scanner.h
+++ b/src/parsing/scanner.h
@@ -21,13 +21,13 @@
 namespace v8 {
 namespace internal {
 
-
 class AstRawString;
 class AstValueFactory;
 class DuplicateFinder;
 class ExternalOneByteString;
 class ExternalTwoByteString;
 class ParserRecorder;
+class RuntimeCallStats;
 class UnicodeCache;
 
 // ---------------------------------------------------------------------
@@ -120,6 +120,11 @@ class Utf16CharacterStream {
   // Returns true if the stream could access the V8 heap after construction.
   virtual bool can_access_heap() const = 0;
 
+  RuntimeCallStats* runtime_call_stats() const { return runtime_call_stats_; }
+  void set_runtime_call_stats(RuntimeCallStats* runtime_call_stats) {
+    runtime_call_stats_ = runtime_call_stats;
+  }
+
  protected:
   Utf16CharacterStream(const uint16_t* buffer_start,
                        const uint16_t* buffer_cursor,
@@ -180,6 +185,7 @@ class Utf16CharacterStream {
   const uint16_t* buffer_cursor_;
   const uint16_t* buffer_end_;
   size_t buffer_pos_;
+  RuntimeCallStats* runtime_call_stats_;
 };
 
 // ----------------------------------------------------------------------------
diff --git a/test/cctest/parsing/test-scanner-streams.cc b/test/cctest/parsing/test-scanner-streams.cc
index 9c8e972c08..bb05231f08 100644
--- a/test/cctest/parsing/test-scanner-streams.cc
+++ b/test/cctest/parsing/test-scanner-streams.cc
@@ -155,7 +155,7 @@ TEST(Utf8StreamAsciiOnly) {
   ChunkSource chunk_source(chunks);
   std::unique_ptr<v8::internal::Utf16CharacterStream> stream(
       v8::internal::ScannerStream::For(
-          &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8, nullptr));
+          &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8));
 
   // Read the data without dying.
   v8::internal::uc32 c;
@@ -173,7 +173,7 @@ TEST(Utf8StreamBOM) {
   ChunkSource chunk_source(chunks);
   std::unique_ptr<v8::internal::Utf16CharacterStream> stream(
       v8::internal::ScannerStream::For(
-          &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8, nullptr));
+          &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8));
 
   // Read the data without tripping over the BOM.
   for (size_t i = 0; unicode_ucs2[i]; i++) {
@@ -207,7 +207,7 @@ TEST(Utf8SplitBOM) {
     ChunkSource chunk_source(chunks);
     std::unique_ptr<v8::internal::Utf16CharacterStream> stream(
         v8::internal::ScannerStream::For(
-            &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8, nullptr));
+            &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8));
 
     // Read the data without tripping over the BOM.
     for (size_t i = 0; unicode_ucs2[i]; i++) {
@@ -223,7 +223,7 @@ TEST(Utf8SplitBOM) {
     ChunkSource chunk_source(chunks);
     std::unique_ptr<v8::internal::Utf16CharacterStream> stream(
         v8::internal::ScannerStream::For(
-            &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8, nullptr));
+            &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8));
 
     // Read the data without tripping over the BOM.
     for (size_t i = 0; unicode_ucs2[i]; i++) {
@@ -238,7 +238,7 @@ TEST(Utf8SplitMultiBOM) {
   ChunkSource chunk_source(chunks);
   std::unique_ptr<i::Utf16CharacterStream> stream(
       v8::internal::ScannerStream::For(
-          &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8, nullptr));
+          &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8));
 
   // Read the data, ensuring we get exactly one of the two BOMs back.
   CHECK_EQ(0xFEFF, stream->Advance());
@@ -260,7 +260,7 @@ TEST(Utf8AdvanceUntil) {
     ChunkSource chunk_source(chunks);
     std::unique_ptr<v8::internal::Utf16CharacterStream> stream(
         v8::internal::ScannerStream::For(
-            &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8, nullptr));
+            &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8));
 
     int32_t res = stream->AdvanceUntil(
         [](int32_t c0_) { return unibrow::IsLineTerminator(c0_); });
@@ -279,14 +279,12 @@ TEST(AdvanceMatchAdvanceUntil) {
 
     std::unique_ptr<v8::internal::Utf16CharacterStream> stream_advance(
         v8::internal::ScannerStream::For(
-            &chunk_source_a, v8::ScriptCompiler::StreamedSource::UTF8,
-            nullptr));
+            &chunk_source_a, v8::ScriptCompiler::StreamedSource::UTF8));
 
     ChunkSource chunk_source_au(chunks);
     std::unique_ptr<v8::internal::Utf16CharacterStream> stream_advance_until(
         v8::internal::ScannerStream::For(
-            &chunk_source_au, v8::ScriptCompiler::StreamedSource::UTF8,
-            nullptr));
+            &chunk_source_au, v8::ScriptCompiler::StreamedSource::UTF8));
 
     int32_t au_c0_ = stream_advance_until->AdvanceUntil(
         [](int32_t c0_) { return unibrow::IsLineTerminator(c0_); });
@@ -328,7 +326,7 @@ TEST(Utf8AdvanceUntilOverChunkBoundaries) {
     ChunkSource chunk_source(chunks);
     std::unique_ptr<v8::internal::Utf16CharacterStream> stream(
         v8::internal::ScannerStream::For(
-            &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8, nullptr));
+            &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8));
 
     int32_t res = stream->AdvanceUntil(
         [](int32_t c0_) { return unibrow::IsLineTerminator(c0_); });
@@ -356,7 +354,7 @@ TEST(Utf8ChunkBoundaries) {
     ChunkSource chunk_source(chunks);
     std::unique_ptr<v8::internal::Utf16CharacterStream> stream(
         v8::internal::ScannerStream::For(
-            &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8, nullptr));
+            &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8));
 
     for (size_t i = 0; unicode_ucs2[i]; i++) {
       CHECK_EQ(unicode_ucs2[i], stream->Advance());
@@ -385,7 +383,7 @@ TEST(Utf8SingleByteChunks) {
     ChunkSource chunk_source(chunks);
     std::unique_ptr<v8::internal::Utf16CharacterStream> stream(
         v8::internal::ScannerStream::For(
-            &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8, nullptr));
+            &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8));
 
     for (size_t j = 0; unicode_ucs2[j]; j++) {
       CHECK_EQ(unicode_ucs2[j], stream->Advance());
@@ -547,14 +545,13 @@ void TestCharacterStreams(const char* one_byte_source, unsigned length,
     ChunkSource single_chunk(data, 1, data_end - data, false);
     std::unique_ptr<i::Utf16CharacterStream> one_byte_streaming_stream(
         i::ScannerStream::For(&single_chunk,
-                              v8::ScriptCompiler::StreamedSource::ONE_BYTE,
-                              nullptr));
+                              v8::ScriptCompiler::StreamedSource::ONE_BYTE));
     TestCharacterStream(one_byte_source, one_byte_streaming_stream.get(),
                         length, start, end);
 
     ChunkSource many_chunks(data, 1, data_end - data, true);
     one_byte_streaming_stream.reset(i::ScannerStream::For(
-        &many_chunks, v8::ScriptCompiler::StreamedSource::ONE_BYTE, nullptr));
+        &many_chunks, v8::ScriptCompiler::StreamedSource::ONE_BYTE));
     TestCharacterStream(one_byte_source, one_byte_streaming_stream.get(),
                         length, start, end);
   }
@@ -565,14 +562,14 @@ void TestCharacterStreams(const char* one_byte_source, unsigned length,
     const uint8_t* data_end = one_byte_vector.end();
     ChunkSource chunks(data, 1, data_end - data, false);
     std::unique_ptr<i::Utf16CharacterStream> utf8_streaming_stream(
-        i::ScannerStream::For(&chunks, v8::ScriptCompiler::StreamedSource::UTF8,
-                              nullptr));
+        i::ScannerStream::For(&chunks,
+                              v8::ScriptCompiler::StreamedSource::UTF8));
     TestCharacterStream(one_byte_source, utf8_streaming_stream.get(), length,
                         start, end);
 
     ChunkSource many_chunks(data, 1, data_end - data, true);
     utf8_streaming_stream.reset(i::ScannerStream::For(
-        &many_chunks, v8::ScriptCompiler::StreamedSource::UTF8, nullptr));
+        &many_chunks, v8::ScriptCompiler::StreamedSource::UTF8));
     TestCharacterStream(one_byte_source, utf8_streaming_stream.get(), length,
                         start, end);
   }
@@ -585,14 +582,14 @@ void TestCharacterStreams(const char* one_byte_source, unsigned length,
         reinterpret_cast<const uint8_t*>(two_byte_vector.end());
     ChunkSource chunks(data, 2, data_end - data, false);
     std::unique_ptr<i::Utf16CharacterStream> two_byte_streaming_stream(
-        i::ScannerStream::For(
-            &chunks, v8::ScriptCompiler::StreamedSource::TWO_BYTE, nullptr));
+        i::ScannerStream::For(&chunks,
+                              v8::ScriptCompiler::StreamedSource::TWO_BYTE));
     TestCharacterStream(one_byte_source, two_byte_streaming_stream.get(),
                         length, start, end);
 
     ChunkSource many_chunks(data, 2, data_end - data, true);
     two_byte_streaming_stream.reset(i::ScannerStream::For(
-        &many_chunks, v8::ScriptCompiler::StreamedSource::TWO_BYTE, nullptr));
+        &many_chunks, v8::ScriptCompiler::StreamedSource::TWO_BYTE));
     TestCharacterStream(one_byte_source, two_byte_streaming_stream.get(),
                         length, start, end);
   }
@@ -634,7 +631,7 @@ TEST(Regress651333) {
     // 65533) instead of the incorrectly coded Latin1 char.
     ChunkSource chunks(bytes, 1, len, false);
     std::unique_ptr<i::Utf16CharacterStream> stream(i::ScannerStream::For(
-        &chunks, v8::ScriptCompiler::StreamedSource::UTF8, nullptr));
+        &chunks, v8::ScriptCompiler::StreamedSource::UTF8));
     for (size_t i = 0; i < len; i++) {
       CHECK_EQ(unicode[i], stream->Advance());
     }
@@ -648,7 +645,7 @@ void TestChunkStreamAgainstReference(
   for (size_t c = 0; c < unicode_expected.size(); ++c) {
     ChunkSource chunk_source(cases[c]);
     std::unique_ptr<i::Utf16CharacterStream> stream(i::ScannerStream::For(
-        &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8, nullptr));
+        &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8));
     for (size_t i = 0; i < unicode_expected[c].size(); i++) {
       CHECK_EQ(unicode_expected[c][i], stream->Advance());
     }
@@ -843,19 +840,17 @@ TEST(CloneCharacterStreams) {
     ChunkSource chunk_source(chunks);
     std::unique_ptr<i::Utf16CharacterStream> one_byte_streaming_stream(
         i::ScannerStream::For(&chunk_source,
-                              v8::ScriptCompiler::StreamedSource::ONE_BYTE,
-                              nullptr));
+                              v8::ScriptCompiler::StreamedSource::ONE_BYTE));
     CHECK(!one_byte_streaming_stream->can_be_cloned());
 
     std::unique_ptr<i::Utf16CharacterStream> utf8_streaming_stream(
-        i::ScannerStream::For(
-            &chunk_source, v8::ScriptCompiler::StreamedSource::UTF8, nullptr));
+        i::ScannerStream::For(&chunk_source,
+                              v8::ScriptCompiler::StreamedSource::UTF8));
     CHECK(!utf8_streaming_stream->can_be_cloned());
 
     std::unique_ptr<i::Utf16CharacterStream> two_byte_streaming_stream(
         i::ScannerStream::For(&chunk_source,
-                              v8::ScriptCompiler::StreamedSource::TWO_BYTE,
-                              nullptr));
+                              v8::ScriptCompiler::StreamedSource::TWO_BYTE));
     CHECK(!two_byte_streaming_stream->can_be_cloned());
   }
 }