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

Source/core/testing/Internals.h

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  * Copyright (C) 2013 Apple 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.
@@ skipping 301 matching lines @@
 
     String textSurroundingNode(Node*, int x, int y, unsigned long maxLength);
 
     void setFocused(bool);
 
     bool ignoreLayoutWithPendingStylesheets(Document*);
 
     void setNetworkStateNotifierTestOnly(bool);
     // Test must call setNetworkStateNotifierTestOnly(true) before calling setNetworkConnectionInfo.
     void setNetworkConnectionInfo(const String&, ExceptionState&);
-    String serializeNavigationMarkup(Document*);
+    String serializeNavigationMarkup();
+    void hideAllTransitionElements();
 
     unsigned countHitRegions(CanvasRenderingContext2D*);
 
 private:
     explicit Internals(Document*);
     Document* contextDocument() const;
     LocalFrame* frame() const;
     Vector<String> iconURLs(Document*, int iconTypesMask) const;
     PassRefPtrWillBeRawPtr<ClientRectList> annotatedRegions(Document*, bool draggable, ExceptionState&);
 
     DocumentMarker* markerAt(Node*, const String& markerType, unsigned index, ExceptionState&);
     RefPtrWillBeMember<InternalRuntimeFlags> m_runtimeFlags;
     RefPtrWillBeMember<InternalProfilers> m_profilers;
 };
 
 } // namespace blink
 
 #endif