Avoid unnecessary invalidations on resize.

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 1534 matching lines @@
 
     bool shouldAnchorAndRescaleViewport = settings()->mainFrameResizesAreOrientationChanges()
         && oldSize.width && oldContentsWidth && newSize.width != oldSize.width;
 
     ViewportAnchor viewportAnchor(&mainFrameImpl()->frame()->eventHandler());
     if (shouldAnchorAndRescaleViewport) {
         viewportAnchor.setAnchor(view->visibleContentRect(),
                                  FloatSize(viewportAnchorXCoord, viewportAnchorYCoord));
     }
 
-    updatePageDefinedViewportConstraints(mainFrameImpl()->frame()->document()->viewportDescription());
-    updateMainFrameLayoutSize();
+    {
+        // Avoids unnecessary invalidations while various bits of state in the FTA are updated.
+        FastTextAutosizer::DeferUpdatePageInfo deferUpdatePageInfo(page());
 
-    WebDevToolsAgentPrivate* agentPrivate = devToolsAgentPrivate();
-    if (agentPrivate)
-        agentPrivate->webViewResized(newSize);
-    WebFrameImpl* webFrame = mainFrameImpl();
-    if (webFrame->frameView()) {
-        webFrame->frameView()->resize(m_size);
-        if (page()->settings().pinchVirtualViewportEnabled())
-            page()->frameHost().pinchViewport().setViewportSize(m_size);
+        updatePageDefinedViewportConstraints(mainFrameImpl()->frame()->document()->viewportDescription());
+        updateMainFrameLayoutSize();
+
+        WebDevToolsAgentPrivate* agentPrivate = devToolsAgentPrivate();
+        if (agentPrivate)
+            agentPrivate->webViewResized(newSize);
+        WebFrameImpl* webFrame = mainFrameImpl();
+        if (webFrame->frameView()) {
+            webFrame->frameView()->resize(m_size);
+            if (page()->settings().pinchVirtualViewportEnabled())
+                page()->frameHost().pinchViewport().setViewportSize(m_size);
+        }
     }
 
     if (settings()->viewportEnabled() && !m_fixedLayoutSizeLock) {
         // Relayout immediately to recalculate the minimum scale limit.
         if (view->needsLayout())
             view->layout();
 
         if (shouldAnchorAndRescaleViewport) {
             float viewportWidthRatio = static_cast<float>(newSize.width) / oldSize.width;
             float contentsWidthRatio = static_cast<float>(contentsSize().width()) / oldContentsWidth;
@@ skipping 2419 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