Manage WebGLRenderingContextBase's weak refs manually without Oilpan.

third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.h

 /*
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 494 matching lines @@
     // Dispatches a context lost event once it is determined that one is needed.
     // This is used for synthetic, WEBGL_lose_context and real context losses. For real ones, it's
     // likely that there's no JavaScript on the stack, but that might be dependent
     // on how exactly the platform discovers that the context was lost. For better
     // portability we always defer the dispatch of the event.
     Timer<WebGLRenderingContextBase> m_dispatchContextLostEventTimer;
     bool m_restoreAllowed;
     Timer<WebGLRenderingContextBase> m_restoreTimer;
 
     bool m_markedCanvasDirty;
-    PersistentHeapHashSetWillBeHeapHashSet<WeakMember<WebGLContextObject>> m_contextObjects;
+#if ENABLE(OILPAN)
+    HeapHashSet<WeakMember<WebGLContextObject>> m_contextObjects;
+#else
+    // The hash set isn't traced, hence the references are effectively
+    // weakly kept. Each WebGLContextObject is responsible for detaching
+    // itself upon finalization if the WebGLRenderingContextBase hasn't been
+    // finalized already and detached them via detachAndRemoveAllObjects().
+    GC_PLUGIN_IGNORE("534524")
+    HashSet<WebGLContextObject*> m_contextObjects;
+#endif
 
     PersistentWillBeMember<WebGLRenderingContextLostCallback> m_contextLostCallbackAdapter;
     PersistentWillBeMember<WebGLRenderingContextErrorMessageCallback> m_errorMessageCallbackAdapter;
 
     // List of bound VBO's. Used to maintain info about sizes for ARRAY_BUFFER and stored values for ELEMENT_ARRAY_BUFFER
     PersistentWillBeMember<WebGLBuffer> m_boundArrayBuffer;
 
     PersistentWillBeMember<WebGLVertexArrayObjectBase> m_defaultVertexArrayObject;
     PersistentWillBeMember<WebGLVertexArrayObjectBase> m_boundVertexArrayObject;
     void setBoundVertexArrayObject(WebGLVertexArrayObjectBase* arrayObject)
@@ skipping 580 matching lines @@
     static IntSize oldestContextSize();
 };
 
 DEFINE_TYPE_CASTS(WebGLRenderingContextBase, CanvasRenderingContext, context, context->is3d(), context.is3d());
 
 } // namespace blink
 
 WTF_ALLOW_MOVE_INIT_AND_COMPARE_WITH_MEM_FUNCTIONS(blink::WebGLRenderingContextBase::TextureUnitState);
 
 #endif // WebGLRenderingContextBase_h