Delegate unique id generation to embedder

This lets embedder to produce an id with sufficient entropy to
facilitate an id appropriate for a multi-process system and
immune to regular RNG seed being overriden, while maintaining
deterministic id allocation for tests.

Design doc: https://docs.google.com/document/d/1vGVWvKP9FTTX6kimcUJR_PAfVgDeIzXXITFpl0SyghQ
Related blink-side change: https://chromium-review.googlesource.com/c/chromium/src/+/2600273

Bug: v8:11268
Change-Id: I1a4d12463cf56d4378859dfa3ee4d717e176d468
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2600442
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Andrey Kosyakov <caseq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71864}

include/v8-inspector.h

@@ -229,6 +229,10 @@ class V8_EXPORT V8InspectorClient {
       const StringView& resourceName) {
     return nullptr;
   }
+
+  // The caller would defer to generating a random 64 bit integer if
+  // this method returns 0.
+  virtual int64_t generateUniqueId() { return 0; }
 };
 
 // These stack trace ids are intended to be passed between debuggers and be

src/inspector/v8-debugger.cc

@@ -68,12 +68,9 @@ V8DebuggerId::V8DebuggerId(std::pair<int64_t, int64_t> pair)
     : m_first(pair.first), m_second(pair.second) {}
 
 // static
-V8DebuggerId V8DebuggerId::generate(v8::Isolate* isolate) {
-  V8DebuggerId debuggerId;
-  debuggerId.m_first = v8::debug::GetNextRandomInt64(isolate);
-  debuggerId.m_second = v8::debug::GetNextRandomInt64(isolate);
-  if (!debuggerId.m_first && !debuggerId.m_second) ++debuggerId.m_first;
-  return debuggerId;
+V8DebuggerId V8DebuggerId::generate(V8InspectorImpl* inspector) {
+  return V8DebuggerId(std::make_pair(inspector->generateUniqueId(),
+                                     inspector->generateUniqueId()));
 }
 
 V8DebuggerId::V8DebuggerId(const String16& debuggerId) {
@@ -1114,7 +1111,7 @@ void V8Debugger::setMaxAsyncTaskStacksForTest(int limit) {
 V8DebuggerId V8Debugger::debuggerIdFor(int contextGroupId) {
   auto it = m_contextGroupIdToDebuggerId.find(contextGroupId);
   if (it != m_contextGroupIdToDebuggerId.end()) return it->second;
-  V8DebuggerId debuggerId = V8DebuggerId::generate(m_isolate);
+  V8DebuggerId debuggerId = V8DebuggerId::generate(m_inspector);
   m_contextGroupIdToDebuggerId.insert(
       it, std::make_pair(contextGroupId, debuggerId));
   return debuggerId;

src/inspector/v8-debugger.h

@@ -50,7 +50,7 @@ class V8DebuggerId {
   V8DebuggerId(const V8DebuggerId&) V8_NOEXCEPT = default;
   ~V8DebuggerId() = default;
 
-  static V8DebuggerId generate(v8::Isolate*);
+  static V8DebuggerId generate(V8InspectorImpl*);
 
   String16 toString() const;
   bool isValid() const;

src/inspector/v8-inspector-impl.cc

@@ -62,7 +62,7 @@ V8InspectorImpl::V8InspectorImpl(v8::Isolate* isolate,
       m_capturingStackTracesCount(0),
       m_lastExceptionId(0),
       m_lastContextId(0),
-      m_isolateId(v8::debug::GetNextRandomInt64(m_isolate)) {
+      m_isolateId(generateUniqueId()) {
   v8::debug::SetInspector(m_isolate, this);
   v8::debug::SetConsoleDelegate(m_isolate, console());
 }
@@ -416,6 +416,13 @@ void V8InspectorImpl::forEachSession(
   }
 }
 
+int64_t V8InspectorImpl::generateUniqueId() {
+  int64_t id = m_client->generateUniqueId();
+  if (!id) id = v8::debug::GetNextRandomInt64(m_isolate);
+  if (!id) id = 1;
+  return id;
+}
+
 V8InspectorImpl::EvaluateScope::EvaluateScope(
     const InjectedScript::Scope& scope)
     : m_scope(scope),

src/inspector/v8-inspector-impl.h

@@ -129,6 +129,7 @@ class V8InspectorImpl : public V8Inspector {
   void forEachSession(
       int contextGroupId,
       const std::function<void(V8InspectorSessionImpl*)>& callback);
+  int64_t generateUniqueId();
 
   class EvaluateScope {
    public:

test/inspector/isolate-data.cc

@@ -487,5 +487,11 @@ std::unique_ptr<v8_inspector::StringBuffer> IsolateData::resourceNameToUrl(
   return std::make_unique<StringBufferImpl>(isolate(), url);
 }
 
+int64_t IsolateData::generateUniqueId() {
+  static int64_t last_unique_id = 0L;
+  // Keep it not too random for tests.
+  return ++last_unique_id;
+}
+
 }  // namespace internal
 }  // namespace v8

test/inspector/isolate-data.h

@@ -130,6 +130,7 @@ class IsolateData : public v8_inspector::V8InspectorClient {
   void maxAsyncCallStackDepthChanged(int depth) override;
   std::unique_ptr<v8_inspector::StringBuffer> resourceNameToUrl(
       const v8_inspector::StringView& resourceName) override;
+  int64_t generateUniqueId() override;
 
   // The isolate gets deleted by its {Dispose} method, not by the default
   // deleter. Therefore we have to define a custom deleter for the unique_ptr to