Make CanvasRenderingContext not inherit from ActiveDOMObject

third_party/WebKit/Source/core/dom/DocumentTest.cpp

 /*
  * Copyright (c) 2014, Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 72 matching lines @@
     {
         return adoptPtrWillBeNoop(new MockDocumentVisibilityObserver(document));
     }
 
     DEFINE_INLINE_VIRTUAL_TRACE()
     {
         DocumentVisibilityObserver::trace(visitor);
     }
 
     MOCK_METHOD1(didChangeVisibilityState, void(PageVisibilityState));
+    MOCK_METHOD0(willDetachDocument, void());
 
 private:
     MockDocumentVisibilityObserver(Document& document) : DocumentVisibilityObserver(document) { }
 };
 
 TEST_F(DocumentTest, VisibilityOberver)
 {
     page().setVisibilityState(PageVisibilityStateVisible, true); // initial state
     OwnPtrWillBeRawPtr<MockDocumentVisibilityObserver> observer1 = MockDocumentVisibilityObserver::create(document());
 
@@ skipping 243 matching lines @@
     EXPECT_NE(previousStyleVersion, document().styleVersion());
 
     document().view()->updateAllLifecyclePhases();
 
     previousStyleVersion = document().styleVersion();
     element->setAttribute(blink::HTMLNames::classAttr, "a b");
     EXPECT_NE(previousStyleVersion, document().styleVersion());
 }
 
 } // namespace blink