[debug,api] Do not use embedder field for debug context id.

We used to reserve the 0-th embedder data field for the debug
context id. This is no longer necessary since the inspector
has migrated to be part of V8. This makes the API a bit simpler.

R=clemensh@chromium.org, jochen@chromium.org, kozyatinskiy@chromium.org
BUG=v8:5530

Review-Url: https://codereview.chromium.org/2806303002
Cr-Commit-Position: refs/heads/master@{#44607}

include/v8.h

@@ -8350,16 +8350,14 @@ class V8_EXPORT Context {
   Isolate* GetIsolate();
 
   /**
-   * The field at kDebugIdIndex is reserved for V8 debugger implementation.
-   * The value is propagated to the scripts compiled in given Context and
-   * can be used for filtering scripts.
+   * The field at kDebugIdIndex used to be reserved for the inspector.
+   * It now serves no purpose.
    */
   enum EmbedderDataFields { kDebugIdIndex = 0 };
 
   /**
    * Gets the embedder data with the given index, which must have been set by a
-   * previous call to SetEmbedderData with the same index. Note that index 0
-   * currently has a special meaning for Chrome's debugger.
+   * previous call to SetEmbedderData with the same index.
    */
   V8_INLINE Local<Value> GetEmbedderData(int index);
 

src/api.cc

@@ -9139,6 +9139,15 @@ MaybeLocal<Array> Debug::GetInternalProperties(Isolate* v8_isolate,
   return debug::GetInternalProperties(v8_isolate, value);
 }
 
+void debug::SetContextId(Local<Context> context, int id) {
+  Utils::OpenHandle(*context)->set_debug_context_id(i::Smi::FromInt(id));
+}
+
+int debug::GetContextId(Local<Context> context) {
+  i::Object* value = Utils::OpenHandle(*context)->debug_context_id();
+  return (value->IsSmi()) ? i::Smi::cast(value)->value() : 0;
+}
+
 Local<Context> debug::GetDebugContext(Isolate* isolate) {
   i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
   ENTER_V8(i_isolate);

src/contexts.h

@@ -240,6 +240,7 @@ enum ContextLookupFlags {
   V(DATA_PROPERTY_DESCRIPTOR_MAP_INDEX, Map, data_property_descriptor_map)     \
   V(DATA_VIEW_FUN_INDEX, JSFunction, data_view_fun)                            \
   V(DATE_FUNCTION_INDEX, JSFunction, date_function)                            \
+  V(DEBUG_CONTEXT_ID_INDEX, Object, debug_context_id)                          \
   V(ERROR_MESSAGE_FOR_CODE_GEN_FROM_STRINGS_INDEX, Object,                     \
     error_message_for_code_gen_from_strings)                                   \
   V(ERRORS_THROWN_INDEX, Smi, errors_thrown)                                   \

src/d8.cc

@@ -642,8 +642,6 @@ class ModuleEmbedderData {
 };
 
 enum {
-  // The debugger reserves the first slot in the Context embedder data.
-  kDebugIdIndex = Context::kDebugIdIndex,
   kModuleEmbedderDataIndex,
   kInspectorClientIndex
 };

src/debug/debug-interface.h

@@ -25,6 +25,9 @@ class Script;
 
 namespace debug {
 
+void SetContextId(Local<Context> context, int id);
+int GetContextId(Local<Context> context);
+
 /**
  * Debugger is running in its own context which is entered while debugger
  * messages are being dispatched. This is an explicit getter for this

src/debug/debug.cc

@@ -2066,8 +2066,7 @@ void Debug::OnAsyncTaskEvent(debug::PromiseDebugActionType type, int id,
 void Debug::ProcessCompileEvent(v8::DebugEvent event, Handle<Script> script) {
   // Attach the correct debug id to the script. The debug id is used by the
   // inspector to filter scripts by native context.
-  FixedArray* array = isolate_->native_context()->embedder_data();
-  script->set_context_data(array->get(v8::Context::kDebugIdIndex));
+  script->set_context_data(isolate_->native_context()->debug_context_id());
   if (ignore_events()) return;
   if (!script->IsUserJavaScript() && script->type() != i::Script::TYPE_WASM) {
     return;

src/inspector/inspected-context.cc

@@ -4,6 +4,7 @@
 
 #include "src/inspector/inspected-context.h"
 
+#include "src/debug/debug-interface.h"
 #include "src/inspector/injected-script.h"
 #include "src/inspector/string-util.h"
 #include "src/inspector/v8-console.h"
@@ -25,8 +26,7 @@ InspectedContext::InspectedContext(V8InspectorImpl* inspector,
       m_auxData(toString16(info.auxData)),
       m_reported(false) {
   v8::Isolate* isolate = m_inspector->isolate();
-  info.context->SetEmbedderData(static_cast<int>(v8::Context::kDebugIdIndex),
-                                v8::Int32::New(isolate, contextId));
+  v8::debug::SetContextId(info.context, contextId);
   v8::Local<v8::Object> global = info.context->Global();
   v8::Local<v8::Object> console =
       m_inspector->console()->createConsole(info.context);
@@ -46,10 +46,7 @@ InspectedContext::~InspectedContext() {
 
 // static
 int InspectedContext::contextId(v8::Local<v8::Context> context) {
-  v8::Local<v8::Value> data =
-      context->GetEmbedderData(static_cast<int>(v8::Context::kDebugIdIndex));
-  if (data.IsEmpty() || !data->IsInt32()) return 0;
-  return static_cast<int>(data.As<v8::Int32>()->Value());
+  return v8::debug::GetContextId(context);
 }
 
 v8::Local<v8::Context> InspectedContext::context() const {

src/runtime/runtime-function.cc

@@ -111,8 +111,7 @@ RUNTIME_FUNCTION(Runtime_FunctionGetContextData) {
   DCHECK_EQ(1, args.length());
 
   CONVERT_ARG_CHECKED(JSFunction, fun, 0);
-  FixedArray* array = fun->native_context()->embedder_data();
-  return array->get(v8::Context::kDebugIdIndex);
+  return fun->native_context()->debug_context_id();
 }
 
 RUNTIME_FUNCTION(Runtime_FunctionSetInstanceClassName) {

src/wasm/wasm-module.cc

@@ -135,8 +135,7 @@ Handle<Script> CreateWasmScript(Isolate* isolate,
                                 const ModuleWireBytes& wire_bytes) {
   Handle<Script> script =
       isolate->factory()->NewScript(isolate->factory()->empty_string());
-  FixedArray* array = isolate->native_context()->embedder_data();
-  script->set_context_data(array->get(v8::Context::kDebugIdIndex));
+  script->set_context_data(isolate->native_context()->debug_context_id());
   script->set_type(Script::TYPE_WASM);
 
   int hash = StringHasher::HashSequentialString(

test/inspector/inspector-impl.cc

@@ -10,7 +10,7 @@
 
 namespace {
 
-const int kInspectorClientIndex = v8::Context::kDebugIdIndex + 1;
+const int kInspectorClientIndex = 0;
 
 class ChannelImpl final : public v8_inspector::V8Inspector::Channel {
  public: