Ensure that if FrameView::isScrollable() is false, the assoc WebLayer is, too.

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 125 matching lines @@
 {
     navigateTo("about:blank");
     forceFullCompositingUpdate();
 
     // Make sure the scrolling coordinator is active.
     FrameView* frameView = m_webViewImpl->mainFrameImpl()->frameView();
     Page* page = m_webViewImpl->mainFrameImpl()->frame()->page();
     ASSERT_TRUE(page->scrollingCoordinator());
     ASSERT_TRUE(page->scrollingCoordinator()->coordinatesScrollingForFrameView(frameView));
 
-    // Fast scrolling should be enabled by default.
+    // Fast scrolling should be enabled by default, BUT if the main frame is
+    // not scrollable, then the rootScrollLayer shouldn't be scrollable either.

[jamesr, 2014/01/06 23:46:01]

can you add a case for what this was originally testing?

     WebLayer* rootScrollLayer = getRootScrollLayer();
-    ASSERT_TRUE(rootScrollLayer->scrollable());
+    ASSERT_FALSE(rootScrollLayer->scrollable());
     ASSERT_FALSE(rootScrollLayer->shouldScrollOnMainThread());
     ASSERT_FALSE(rootScrollLayer->haveWheelEventHandlers());
 }
 
 static WebLayer* webLayerFromElement(Element* element)
 {
     if (!element)
         return 0;
     RenderObject* renderer = element->renderer();
     if (!renderer || !renderer->isBoxModelObject())
@@ skipping 310 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