Update WebViewImpl::contentsPreferredMinimumSize to be agnostic to the scrolling element

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 3379 matching lines @@
         return IntSize();
     LayoutView* root = page()->deprecatedLocalMainFrame()->contentLayoutObject();
     if (!root)
         return IntSize();
     return root->documentRect().size();
 }
 
 WebSize WebViewImpl::contentsPreferredMinimumSize()
 {
     Document* document = m_page->mainFrame()->isLocalFrame() ? m_page->deprecatedLocalMainFrame()->document() : 0;
-    if (!document || !document->layoutView() || !document->documentElement())
+    if (!document || !document->layoutView() || !document->documentElement() || !document->documentElement()->layoutBox())
         return WebSize();
 
     layout();
     int widthScaled = document->layoutView()->minPreferredLogicalWidth().round(); // Already accounts for zoom.
-    int heightScaled = static_cast<int>((document->documentElement()->scrollHeight() * zoomLevelToZoomFactor(zoomLevel())) + 0.5); // +0.5 to round rather than truncating
+    int heightScaled = document->documentElement()->layoutBox()->scrollHeight().round();
     return IntSize(widthScaled, heightScaled);
 }
 
 void WebViewImpl::enableViewport()
 {
     settings()->setViewportEnabled(true);
 }
 
 void WebViewImpl::disableViewport()
 {
@@ skipping 1085 matching lines @@
     if (m_pageColorOverlay)
         m_pageColorOverlay->update();
     if (m_inspectorOverlay) {
         PageOverlay* inspectorPageOverlay = m_inspectorOverlay->pageOverlay();
         if (inspectorPageOverlay)
             inspectorPageOverlay->update();
     }
 }
 
 } // namespace blink