Implement WEBGL_shared_resources

Source/core/html/canvas/WebGLObject.h

Index: Source/core/html/canvas/WebGLObject.h
diff --git a/Source/core/html/canvas/WebGLObject.h b/Source/core/html/canvas/WebGLObject.h
index a3a9f86376b469d90cb4ce2007a631b3326a8a43..1b9bdd6bbd21a7e50ff0f78a23de127e01dbaf4a 100644
--- a/Source/core/html/canvas/WebGLObject.h
+++ b/Source/core/html/canvas/WebGLObject.h
@@ -56,9 +56,6 @@ public:
     // 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 WebGLRenderingContext*) const = 0;
-
 protected:
     WebGLObject(WebGLRenderingContext*);
 
@@ -72,6 +69,9 @@ protected:
 
     virtual void detach();
 
+    // Warning!!!: This can only be used on object delete. Using it for
+    // other purposes will mess up shared resources because the changes
+    // will take place on the wrong context.
     virtual GraphicsContext3D* getAGraphicsContext3D() const = 0;
 
 private: