Oilpan: add [WillBeGarbageCollected] for Node.

Source/web/tests/ScrollingCoordinatorChromiumTest.cpp

 /*
  * Copyright (C) 2012 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:
  * 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 240 matching lines @@
 }
 
 TEST_F(ScrollingCoordinatorChromiumTest, updateEventHandlersDuringTeardown)
 {
     registerMockedHttpURLLoad("scroll-event-handler-window.html");
     navigateTo(m_baseURL + "scroll-event-handler-window.html");
     forceFullCompositingUpdate();
 
     // Simulate detaching the document from its DOM window. This should not
     // cause a crash when the WebViewImpl is closed by the test runner.
-    frame()->document()->clearDOMWindow();
+    frame()->document()->prepareForDestruction();
 }
 
 TEST_F(ScrollingCoordinatorChromiumTest, clippedBodyTest)
 {
     registerMockedHttpURLLoad("clipped-body.html");
     navigateTo(m_baseURL + "clipped-body.html");
     forceFullCompositingUpdate();
 
     WebLayer* rootScrollLayer = getRootScrollLayer();
     ASSERT_EQ(0u, rootScrollLayer->nonFastScrollableRegion().size());
@@ skipping 180 matching lines @@
 TEST_F(ScrollingCoordinatorChromiumTest, setupScrollbarLayerShouldNotCrash)
 {
     registerMockedHttpURLLoad("setup_scrollbar_layer_crash.html");
     navigateTo(m_baseURL + "setup_scrollbar_layer_crash.html");
     forceFullCompositingUpdate();
     // This test document setup an iframe with scrollbars, then switch to
     // an empty document by javascript.
 }
 
 } // namespace