Add a callback from Blink to Chromium for when page scale changes

Source/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 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:
  *
  *     * 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 4107 matching lines @@
 void WebViewImpl::didChangeContentsSize()
 {
     m_pageScaleConstraintsSet.didChangeContentsSize(contentsSize(), pageScaleFactor());
 }
 
 void WebViewImpl::pageScaleFactorChanged()
 {
     m_pageScaleConstraintsSet.setNeedsReset(false);
     updateLayerTreeViewport();
     m_page->inspectorController().pageScaleFactorChanged();
+    m_client->pageScaleFactorChanged();
 }
 
 bool WebViewImpl::useExternalPopupMenus()
 {
     return shouldUseExternalPopupMenus;
 }
 
 void WebViewImpl::startDragging(LocalFrame* frame,
                                 const WebDragData& dragData,
                                 WebDragOperationsMask mask,
@@ skipping 533 matching lines @@
     return mainFrameImpl()->frameView()->layoutSize().width() == m_size.width
         || (constraints.minimumScale == constraints.maximumScale && constraints.minimumScale != -1);
 }
 
 void WebViewImpl::forceNextWebGLContextCreationToFail()
 {
     WebGLRenderingContext::forceNextWebGLContextCreationToFail();
 }
 
 } // namespace blink