Trace ScriptWrappableVisitor.m_markingDeque by oilpan gc

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

Index: third_party/WebKit/Source/bindings/core/v8/ActiveScriptWrappable.cpp
diff --git a/third_party/WebKit/Source/bindings/core/v8/ActiveScriptWrappable.cpp b/third_party/WebKit/Source/bindings/core/v8/ActiveScriptWrappable.cpp
index f474df72e42c419b4e16b92208eca9f24315aa73..16ac4fc65b0cbfb50838f4fc8a92975b841f00c7 100644
--- a/third_party/WebKit/Source/bindings/core/v8/ActiveScriptWrappable.cpp
+++ b/third_party/WebKit/Source/bindings/core/v8/ActiveScriptWrappable.cpp
@@ -28,10 +28,13 @@ void ActiveScriptWrappable::traceActiveScriptWrappables(v8::Isolate* isolate, Sc
     }
 
     for (auto activeWrappable : *activeScriptWrappables) {
-        if (!activeWrappable->hasPendingActivity())
+        if (!activeWrappable->hasPendingActivity()) {
             continue;
+        }
 
-        activeWrappable->toScriptWrappable()->traceWrappers(visitor);
+        auto scriptWrappable = activeWrappable->toScriptWrappable();
+        auto wrapperTypeInfo = const_cast<WrapperTypeInfo*>(scriptWrappable->wrapperTypeInfo());
+        visitor->RegisterV8Reference(std::make_pair(wrapperTypeInfo, scriptWrappable));

[haraken, 2016/06/08 14:38:23]

Would you help me understand why you need to push ActiveScriptWrappables to the
marking deque?

I'm assuming that traceActiveScriptWrappables should be called multiple times in
the incremental marking phase because the pending activity may change over time.

[Marcel Hlopko, 2016/06/08 15:12:48]

Here it's just for the consistency. Objects external to ScriptWrappableVisitor
can only add to the deque, cannot initiate tracing. Tracing is initiated only by
AdvanceTracing.

However you are correct that traceActiveScriptWrappables will be called multiple
times. Once during TracePrologue, as an overapproximation, and then at the
"atomic pause of wrapper tracing".

     }
 }