Trace ScriptWrappableVisitor.m_markingDeque by oilpan gc

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "bindings/core/v8/ActiveScriptWrappable.h"
 
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "bindings/core/v8/ScriptWrappableVisitor.h"
 #include "bindings/core/v8/V8PerIsolateData.h"
 
@@ skipping 10 matching lines @@
 
 void ActiveScriptWrappable::traceActiveScriptWrappables(v8::Isolate* isolate, ScriptWrappableVisitor* visitor)
 {
     V8PerIsolateData* isolateData = V8PerIsolateData::from(isolate);
     auto activeScriptWrappables = isolateData->activeScriptWrappables();
     if (!activeScriptWrappables) {
         return;
     }
 
     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".

     }
 }
 
 } // namespace blink