[wrapper-tracing] Reduce marking overhead: Tri-color marking without 3 colors

third_party/WebKit/Source/bindings/core/v8/ScriptWrappableVisitor.h

Index: third_party/WebKit/Source/bindings/core/v8/ScriptWrappableVisitor.h
diff --git a/third_party/WebKit/Source/bindings/core/v8/ScriptWrappableVisitor.h b/third_party/WebKit/Source/bindings/core/v8/ScriptWrappableVisitor.h
index 4387453a1a95c286f4861558a09be8e9fc4ce926..31e9252b4433d0f0f5044c1d930cb9d86fbf716c 100644
--- a/third_party/WebKit/Source/bindings/core/v8/ScriptWrappableVisitor.h
+++ b/third_party/WebKit/Source/bindings/core/v8/ScriptWrappableVisitor.h
@@ -126,12 +126,23 @@ class CORE_EXPORT ScriptWrappableVisitor : public v8::EmbedderHeapTracer,
     // objects or if we are outside of object construction.
     if (!IsGarbageCollectedMixin<T>::value ||
         !threadState->isMixinInConstruction()) {
+      // If the wrapper is already marked we can bail out here.
       if (TraceTrait<T>::heapObjectHeader(dstObject)->isWrapperHeaderMarked())
         return;
+      // Otherwise, eagerly mark the wrapper header and put the object on the
+      // marking deque for further processing.
+      WrapperVisitor* const visitor = currentVisitor(threadState->isolate());
+      TraceTrait<T>::markWrapperHeaderOnly(visitor, dstObject);
+      visitor->pushToMarkingDeque(TraceTrait<T>::traceMarkedWrapper,
+                                  TraceTrait<T>::heapObjectHeader, dstObject);
+      return;
     }
 
+    // We cannot eagerly mark the wrapper header because of mixin
+    // construction. Delay further processing until AdvanceMarking, which has to
+    // be in a non-construction state. This path may result in duplicates.
     currentVisitor(threadState->isolate())
-        ->pushToMarkingDeque(TraceTrait<T>::markWrapper,
+        ->pushToMarkingDeque(TraceTrait<T>::markAndTraceWrapper,

[haraken, 2016/12/21 01:38:37]

I don't have any strong opinion about the naming, but if you want to be
consistent with oilpan:

  markAndTraceWrapper => markWrapper
  markWrapperHeaderOnly => markNoTracing (Oilpan already have the notion)

[Michael Lippautz, 2016/12/21 09:31:08]

I realize I am diverging a bit with oilpan, but I'd like to name them:
- markAndTraceWrapper
- markWrapperNoTracing 
- traceMarkedWrapper

These names describe exactly what is happening :)

                              TraceTrait<T>::heapObjectHeader, dstObject);
   }