Remove WebGLObject maps from WebGLRenderingContextBase and WebGLContextGroup.

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

 /*
  * Copyright (C) 2011 Apple Inc. All rights reserved.
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  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
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  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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 #ifndef WebGLContextGroup_h
 #define WebGLContextGroup_h
 
+#include "bindings/core/v8/ScriptWrappable.h"
 #include "modules/webgl/WebGLRenderingContextBase.h"
 #include "wtf/HashSet.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefCounted.h"
 
 namespace blink {
 
-class WebGLSharedObject;
-class WebGLRenderingContextBase;
-
 typedef int ExceptionCode;
 
-class WebGLContextGroup final : public RefCounted<WebGLContextGroup> {
+class WebGLContextGroup final : public GarbageCollected<WebGLContextGroup>,
+                                public TraceWrapperBase {
+  WTF_MAKE_NONCOPYABLE(WebGLContextGroup);
+
  public:
-  static PassRefPtr<WebGLContextGroup> create();
-  ~WebGLContextGroup();
+  WebGLContextGroup();
 
   void addContext(WebGLRenderingContextBase*);
-  void removeContext(WebGLRenderingContextBase*);
 
-  void addObject(WebGLSharedObject*);
-  void removeObject(WebGLSharedObject*);
+  // There's no point in having a removeContext method any more now that
+  // the context group is GarbageCollected. The only time it would be
+  // called would be during WebGLRenderingContext destruction, and at that
+  // time, the context is not allowed to refer back to the context group
+  // since both are on the Oilpan heap.
 
   gpu::gles2::GLES2Interface* getAGLInterface();
 
   void loseContextGroup(WebGLRenderingContextBase::LostContextMode,
                         WebGLRenderingContextBase::AutoRecoveryMethod);
 
+  // This counter gets incremented every time context loss is
+  // triggered. Because there's no longer any explicit enumeration of
+  // the objects in a given context group upon context loss, each
+  // object needs to keep track of the context loss count when it was
+  // created, in order to validate itself.
+  uint32_t numberOfContextLosses() const;
+
+  DEFINE_INLINE_TRACE() { visitor->trace(m_contexts); }
+
+  DECLARE_VIRTUAL_TRACE_WRAPPERS();
+
  private:
   friend class WebGLObject;
 
-  WebGLContextGroup();
+  uint32_t m_numberOfContextLosses;
 
-  void detachAndRemoveAllObjects();
-
-  // FIXME: Oilpan: this object is not on the heap, but keeps untraced
-  // pointers to on-heap objects in the two hash sets below.
-  // The objects are responsible for managing their
-  // registration with WebGLContextGroup, and vice versa, the
-  // WebGLContextGroup takes care of detaching the group objects if
-  // the set of WebGLRenderingContextBase contexts becomes empty.
-  HashSet<UntracedMember<WebGLRenderingContextBase>> m_contexts;
-  HashSet<UntracedMember<WebGLSharedObject>> m_groupObjects;
+  // Note: ideally this would use a TraceWrapperMember subclass, but
+  // that doesn't seem to exist for weak members yet.
+  HeapHashSet<WeakMember<WebGLRenderingContextBase>> m_contexts;
 };
 
 }  // namespace blink
 
 #endif  // WebGLContextGroup_h