Remove WebGLObject maps from WebGLRenderingContextBase and WebGLContextGroup.

third_party/WebKit/Source/modules/webgl/WebGLObject.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 42 matching lines @@
   GLuint result = object->object();
   DCHECK(result);
   return result;
 }
 
 class WebGLObject : public GarbageCollectedFinalized<WebGLObject>,
                     public ScriptWrappable {
   WTF_MAKE_NONCOPYABLE(WebGLObject);
 
  public:
+  // We can't call virtual functions like deleteObjectImpl in this class's
+  // destructor; doing so results in a pure virtual function call. Further,
+  // making this destructor non-virtual is complicated with respect to
+  // Oilpan tracing. Therefore this destructor is declared virtual, but is
+  // empty, and the code that would have gone into its body is called by
+  // subclasses via runDestructor().
   virtual ~WebGLObject();
 
   // deleteObject may not always delete the OpenGL resource.  For programs and
   // shaders, deletion is delayed until they are no longer attached.
   // FIXME: revisit this when resource sharing between contexts are implemented.
   void deleteObject(gpu::gles2::GLES2Interface*);
 
   void onAttached() { ++m_attachmentCount; }
   void onDetached(gpu::gles2::GLES2Interface*);
 
   // This indicates whether the client side issue a delete call already, not
   // whether the OpenGL resource is deleted.
   // object()==0 indicates the OpenGL resource is deleted.
   bool isDeleted() { return m_deleted; }
 
   // True if this object belongs to the group or context.
   virtual bool validate(const WebGLContextGroup*,
                         const WebGLRenderingContextBase*) const = 0;
   virtual bool hasObject() const = 0;
 
+  // WebGLObjects are eagerly finalized, and the WebGLRenderingContextBase
+  // is specifically not. This is done in order to allow WebGLObjects to
+  // refer back to their owning context in their destructor to delete their
+  // resources if they are GC'd before the context is.
+  EAGERLY_FINALIZE();
+  DECLARE_EAGER_FINALIZATION_OPERATOR_NEW();

[haraken, 2016/12/05 05:15:59]

Do you need this macro?

[Ken Russell (switch to Gerrit), 2016/12/05 06:03:40]

Yes, we absolutely do. The entire point of this CL is to make WebGLObject
eagerly finalized before its context or context group, so that it has the
opportunity to use that context to delete itself, if the context isn't also
being destroyed. This is critical to ensure prompt reclamation of graphics
resources if the programmer loses references to potentially-expensive objects
like WebGLBuffer or WebGLTexture.

[haraken, 2016/12/05 06:08:40]

EAGERLY_FINALIZE() is needed but DECLARE_EAGER_FINALIZATION_OPERATOR_NEW() won't
be needed.

[Ken Russell (switch to Gerrit), 2016/12/05 06:36:20]

Thanks for the clarification. Will fix. (Is there any documentation for this?
https://chromium.googlesource.com/chromium/src/+/master/third_party/WebKit/So...
is empty.)

+
   DEFINE_INLINE_VIRTUAL_TRACE() {}
 
+  DECLARE_VIRTUAL_TRACE_WRAPPERS();
+
  protected:
   // To allow WebGL[2]RenderingContextBase to call visitChildDOMWrappers.
   friend class WebGLRenderingContextBase;
   friend class WebGL2RenderingContextBase;
 
   explicit WebGLObject(WebGLRenderingContextBase*);
 
   // deleteObjectImpl should be only called once to delete the OpenGL resource.
   // After calling deleteObjectImpl, hasObject() should return false.
   virtual void deleteObjectImpl(gpu::gles2::GLES2Interface*) = 0;
 
   virtual bool hasGroupOrContext() const = 0;
 
+  // Return the current number of context losses associated with this
+  // object's context group (if it's a shared object), or its
+  // context's context group (if it's a per-context object).
+  virtual uint32_t currentNumberOfContextLosses() const = 0;
+
+  uint32_t cachedNumberOfContextLosses() const;
+
   void detach();
   void detachAndDeleteObject();
 
   virtual gpu::gles2::GLES2Interface* getAGLInterface() const = 0;
 
   virtual void visitChildDOMWrappers(v8::Isolate*,
                                      const v8::Persistent<v8::Object>&) {}
 
+  // Used by leaf subclasses to run the destruction sequence -- what would
+  // be in the destructor of the base class, if it could be. Must be called
+  // no more than once.
+  void runDestructor();
+
+  // Indicates to subclasses that the destructor is being run.
+  bool destructionInProgress() const;
+
  private:
+  // This was the number of context losses of the object's associated
+  // WebGLContextGroup at the time this object was created. Contexts
+  // no longer refer to all the objects that they ever created, so
+  // it's necessary to check this count when validating each object.
+  uint32_t m_cachedNumberOfContextLosses;
+
   unsigned m_attachmentCount;
+
+  // Indicates whether the WebGL context's deletion function for this
+  // object (deleteBuffer, deleteTexture, etc.) has been called.
   bool m_deleted;
+
+  // Indicates whether the destructor has been entered and we therefore
+  // need to be careful in subclasses to not touch other on-heap objects.
+  bool m_destructionInProgress;
 };
 
 }  // namespace blink
 
 #endif  // WebGLObject_h