[Pinch-to-zoom] Moved scale factor into PinchViewport

Source/core/frame/FrameHost.h

 /*
  * Copyright (C) 2013 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 56 matching lines @@
     Settings& settings() const;
     Chrome& chrome() const;
     PageConsole& console() const;
     UseCounter& useCounter() const;
 
     // Corresponds to pixel density of the device where this Page is
     // being displayed. In multi-monitor setups this can vary between pages.
     // This value does not account for Page zoom, use LocalFrame::devicePixelRatio instead.
     float deviceScaleFactor() const;
 
-    PinchViewport& pinchViewport();
+    PinchViewport& pinchViewport() const;
 
 private:
     explicit FrameHost(Page&);
 
     Page& m_page;
     const OwnPtr<PageConsole> m_console;
-    PinchViewport m_pinchViewport;
+    const OwnPtr<PinchViewport> m_pinchViewport;
 };
 
 }
 
 #endif // FrameHost_h