Navigation transitions: Hide transition elements by setting CSS opacity rather than display.

Source/web/tests/WebDocumentTest.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 
 #include "public/web/WebDocument.h"
 
 #include "core/CSSPropertyNames.h"
 #include "core/dom/NodeRenderStyle.h"
@@ skipping 80 matching lines @@
     ASSERT_EQ(Color(0, 0, 0), bodyStyle->visitedDependentColor(blink::CSSPropertyColor));
 
     frame->document().beginExitTransition("#foo");
 
     // Make sure the stylesheet load request gets processed.
     FrameTestHelpers::pumpPendingRequestsDoNotUse(frame);
     coreDoc->updateRenderTreeIfNeeded();
 
     // The element should now be hidden.
     transitionStyle = transitionElement->renderStyle();
-    ASSERT_FALSE(transitionStyle);
+    ASSERT_TRUE(transitionStyle);
+    ASSERT_EQ(transitionStyle->opacity(), 0);
 
     // The stylesheet should now have been applied.
     bodyStyle = bodyElement->renderStyle();
     ASSERT(bodyStyle);
     ASSERT_EQ(Color(0, 128, 0), bodyStyle->visitedDependentColor(blink::CSSPropertyColor));
 }
 
 }