[wrapper-tracing] Add heap snapshot generator infrastructure

third_party/WebKit/Source/bindings/core/v8/V8GCController.cpp

Index: third_party/WebKit/Source/bindings/core/v8/V8GCController.cpp
diff --git a/third_party/WebKit/Source/bindings/core/v8/V8GCController.cpp b/third_party/WebKit/Source/bindings/core/v8/V8GCController.cpp
index 6ded783a981de097db3e6563388ac6f197bae47a..2596482954ad967612566ecaf5c798d76fb613e5 100644
--- a/third_party/WebKit/Source/bindings/core/v8/V8GCController.cpp
+++ b/third_party/WebKit/Source/bindings/core/v8/V8GCController.cpp
@@ -148,6 +148,99 @@ class MinorGCUnmodifiedWrapperVisitor : public v8::PersistentHandleVisitor {
   v8::Isolate* m_isolate;
 };
 
+class HeapSnaphotWrapperVisitor : public ScriptWrappableVisitor {
+ public:
+  explicit HeapSnaphotWrapperVisitor(v8::Isolate* isolate)
+      : ScriptWrappableVisitor(isolate) {}
+
+  // Trace through the blink heap to find all V8 wrappers reachable from
+  // ActiveScriptWrappables.
+  WTF::HashSet<const v8::PersistentBase<v8::Value>*> findPendingWrappers() {
+    m_foundV8Wrappers.clear();
+
+    TracePrologue();
+    ActiveScriptWrappableBase::traceActiveScriptWrappables(m_isolate, this);
+    AdvanceTracing(
+        0,
+        v8::EmbedderHeapTracer::AdvanceTracingActions(
+            v8::EmbedderHeapTracer::ForceCompletionAction::FORCE_COMPLETION));
+    // Abort instead of Epilogue as we want to finish synchronously.
+    AbortTracing();
+
+    return std::move(m_foundV8Wrappers);
+  }
+
+  // Trace through the blink heap to find all V8 wrappers reachable from
+  // |traceable|.
+  WTF::HashSet<const v8::PersistentBase<v8::Value>*>
+  findV8WrappersReachableFrom(ScriptWrappable* traceable) {
+    m_foundV8Wrappers.clear();
+
+    TracePrologue();
+    traceable->wrapperTypeInfo()->traceWrappers(this, traceable);
+    AdvanceTracing(
+        0,
+        v8::EmbedderHeapTracer::AdvanceTracingActions(
+            v8::EmbedderHeapTracer::ForceCompletionAction::FORCE_COMPLETION));
+    // Abort instead of Epilogue as we want to finish synchronously.
+    AbortTracing();
+
+    return std::move(m_foundV8Wrappers);
+  }
+
+  void markWrapper(const v8::PersistentBase<v8::Value>* value) const override {
+    if (!m_tracingInProgress || m_foundV8Wrappers.contains(value))
+      return;
+    m_foundV8Wrappers.add(value);
+  }
+
+ private:
+  mutable WTF::HashSet<const v8::PersistentBase<v8::Value>*> m_foundV8Wrappers;

[alph, 2017/01/12 08:59:00]

I wonder why not std::unordered_set ?

[Michael Lippautz, 2017/01/12 12:23:19]

Done. Actually I changed the API type to unodred_set so that we can move rather
than copy.

+};
+
+class HeapSnapshotHandlesVisitor : public v8::PersistentHandleVisitor {
+ public:
+  explicit HeapSnapshotHandlesVisitor(v8::Isolate* isolate) {}
+
+  void VisitPersistentHandle(v8::Persistent<v8::Value>* value,
+                             uint16_t classId) override {
+    // TODO: Fill m_nodesRequiringTracing.
+  }
+
+  WTF::HashSet<UntracedMember<Node>> nodesRequiringTracing() {
+    return std::move(m_nodesRequiringTracing);
+  }
+
+ private:
+  WTF::HashSet<UntracedMember<Node>> m_nodesRequiringTracing;
+};
+
+v8::HeapProfiler::RetainerInfos V8GCController::getRetainerInfos(
+    v8::Isolate* isolate) {
+  v8::HeapProfiler::RetainerInfos infos;
+  HeapSnaphotWrapperVisitor tracer(isolate);
+
+  // Find wrappers for pending activities.
+  {
+    V8PerIsolateData::TemporaryScriptWrappableVisitorScope scope(isolate,
+                                                                 &tracer);
+    std::vector<const v8::PersistentBase<v8::Value>*> wrappers;
+    for (auto& wrapper : tracer.findPendingWrappers()) {
+      wrappers.push_back(wrapper);
+    }
+    infos.push_back(std::make_pair(new SuspendableObjectsInfo(wrappers.size()),
+                                   std::move(wrappers)));
+  }
+
+  // Find wrappers for DOM trees.
+  {
+    HeapSnapshotHandlesVisitor visitor(isolate);
+    // TODO
+  }
+
+  return infos;
+}
+
 class MajorGCWrapperVisitor : public v8::PersistentHandleVisitor {
  public:
   explicit MajorGCWrapperVisitor(v8::Isolate* isolate,