Don't calculate a top controls adjustment if pinch viewport size is uninitialized.

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 1711 matching lines @@
         return;
 
     float topControlsViewportAdjustment = m_topControlsLayoutHeight - m_topControlsContentOffset;
     if (!pinchVirtualViewportEnabled()) {
         // The viewport bounds were adjusted on the compositor by this much due to top controls. Tell
         // the FrameView about it so it can make correct scroll offset clamping decisions during compositor
         // commits.
         view->setTopControlsViewportAdjustment(topControlsViewportAdjustment);
     } else {
         PinchViewport& pinchViewport = page()->frameHost().pinchViewport();
+
+        if (!pinchViewport.visibleRect().width() || !pinchViewport.visibleRect().height())

[Peter Kasting, 2014/10/22 19:32:21]

Can this just be "if (pinchViewport.visibleRect().isEmpty())"?  Or did you
actually want negative-size cases to proceed onwards?

[bokan, 2014/10/22 20:08:53]

Done.

+            return;
+
         pinchViewport.setTopControlsAdjustment(topControlsViewportAdjustment);
 
         // Shrink the FrameView by the amount that will maintain the aspect-ratio with the PinchViewport.
         float aspectRatio = pinchViewport.visibleRect().width() / pinchViewport.visibleRect().height();
         float newHeight = view->unscaledVisibleContentSize(ExcludeScrollbars).width() / aspectRatio;
         float adjustment = newHeight - view->unscaledVisibleContentSize(ExcludeScrollbars).height();
         view->setTopControlsViewportAdjustment(adjustment);
     }
 }
 
@@ skipping 2726 matching lines @@
     const PageScaleConstraints& constraints = m_pageScaleConstraintsSet.pageDefinedConstraints();
 
     if (!mainFrameImpl() || !mainFrameImpl()->frameView())
         return false;
 
     return mainFrameImpl()->frameView()->layoutSize().width() == m_size.width
         || (constraints.minimumScale == constraints.maximumScale && constraints.minimumScale != -1);
 }
 
 } // namespace blink