Avoid unnecessary invalidations on resize.

Source/core/rendering/FastTextAutosizer.cpp

 /*
  * 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 218 matching lines @@
     return isIndependentDescendant(block) || mightBeWiderOrNarrowerDescendant(block) || block->isTable();
 }
 
 FastTextAutosizer::FastTextAutosizer(const Document* document)
     : m_document(document)
     , m_frameWidth(0)
     , m_layoutWidth(0)
     , m_baseMultiplier(0)
     , m_pageNeedsAutosizing(false)
     , m_previouslyAutosized(false)
+    , m_updatePageInfoDeferred(false)
     , m_firstBlock(0)
 #ifndef NDEBUG
     , m_blocksThatHaveBegunLayout()
 #endif
     , m_superclusters()
     , m_clusterStack()
     , m_fingerprintMapper()
 {
 }
 
@@ skipping 34 matching lines @@
 #ifndef NDEBUG
         m_blocksThatHaveBegunLayout.add(block);
 #endif
         if (Cluster* cluster = maybeCreateCluster(block))
             m_clusterStack.append(adoptPtr(cluster));
     }
 }
 
 void FastTextAutosizer::beginLayout(RenderBlock* block)
 {
-    ASSERT(enabled() && m_pageNeedsAutosizing);
+    ASSERT(enabled() && m_pageNeedsAutosizing && !m_updatePageInfoDeferred);
 #ifndef NDEBUG
     m_blocksThatHaveBegunLayout.add(block);
 #endif
 
     if (!m_firstBlock)  {
         m_firstBlock = block;
         prepareClusterStack(block->parent());
     } else if (block == currentCluster()->m_root) {
         // Ignore beginLayout on the same block twice.
         // This can happen with paginated overflow.
@@ skipping 128 matching lines @@
     ASSERT(m_document->frame()->isMainFrame());
 
     for (LocalFrame* frame = m_document->frame(); frame; frame = frame->tree().traverseNext()) {
         if (FastTextAutosizer* textAutosizer = frame->document()->fastTextAutosizer())
             textAutosizer->updatePageInfo();
     }
 }
 
 void FastTextAutosizer::updatePageInfo()
 {
-    if (!enabled())
+    if (!enabled() || m_updatePageInfoDeferred)
         return;
 
     int previousFrameWidth = m_frameWidth;
     int previousLayoutWidth = m_layoutWidth;
     float previousBaseMultiplier = m_baseMultiplier;
 
     RenderView* renderView = toRenderView(m_document->renderer());
     bool horizontalWritingMode = isHorizontalWritingMode(renderView->style()->writingMode());
 
     LocalFrame* mainFrame = m_document->page()->mainFrame();
@@ skipping 527 matching lines @@
     else
         m_textAutosizer = 0;
 }
 
 FastTextAutosizer::LayoutScope::~LayoutScope()
 {
     if (m_textAutosizer)
         m_textAutosizer->endLayout(m_block);
 }
 
+FastTextAutosizer::DeferUpdatePageInfo::DeferUpdatePageInfo(Page* page)
+    : m_mainFrame(page->mainFrame())
+{
+    if (!m_mainFrame)
+        return;
+
+    if (FastTextAutosizer* textAutosizer = m_mainFrame->document()->fastTextAutosizer())
+        textAutosizer->m_updatePageInfoDeferred = true;
+}
+
+FastTextAutosizer::DeferUpdatePageInfo::~DeferUpdatePageInfo()
+{

[pdr., 2014/03/25 22:23:45]

Should we bail here if !m_mainFrame?

[skobes, 2014/03/26 00:36:50]

Good catch, done.

+    if (FastTextAutosizer* textAutosizer = m_mainFrame->document()->fastTextAutosizer()) {

[pdr., 2014/03/25 22:23:45]

I'm a little worried about use-after-frees of m_mainFrame (e.g., see comment in
DOMWindow::find). Can m_mainFrame be a refptr?

[skobes, 2014/03/26 00:36:50]

Done.

+        textAutosizer->m_updatePageInfoDeferred = false;
+        textAutosizer->updatePageInfoInAllFrames();
+    }
+}
+
 } // namespace WebCore