Optimize layout/repaint on FrameView resize

Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 924 matching lines @@
                 setScrollbarsSuppressed(false, true);
             } else if (hMode != currentHMode || vMode != currentVMode) {
                 setScrollbarModes(hMode, vMode);
             }
 
             LayoutSize oldSize = m_size;
 
             m_size = LayoutSize(layoutSize().width(), layoutSize().height());
 
             if (oldSize != m_size) {
-                shouldDoFullLayout = true;
+                if (!renderView()->needsResizeLayoutOnly()
+                    || (renderView()->style()->isHorizontalWritingMode()
+                        ? (oldSize.width() != m_size.width()) : (oldSize.height() != m_size.height())))
+                    shouldDoFullLayout = true;
+
                 if (!m_firstLayout) {
                     RenderBox* rootRenderer = document->documentElement() ? document->documentElement()->renderBox() : 0;
                     RenderBox* bodyRenderer = rootRenderer && document->body() ? document->body()->renderBox() : 0;
                     if (bodyRenderer && bodyRenderer->stretchesToViewport())
                         bodyRenderer->setChildNeedsLayout();
                     else if (rootRenderer && rootRenderer->stretchesToViewport())
                         rootRenderer->setChildNeedsLayout();
                 }
             }
         }
@@ skipping 783 matching lines @@
         repaintRect.move(-scrollOffset());
         m_trackedRepaintRects.append(repaintRect);
     }
 
     ScrollView::repaintContentRectangle(r);
 }
 
 void FrameView::contentsResized()
 {
     ScrollView::contentsResized();
-    setNeedsLayout();
+    setNeedsResizeLayout();
 }
 
 void FrameView::scrollbarExistenceDidChange()
 {
     // We check to make sure the view is attached to a frame() as this method can
     // be triggered before the view is attached by LocalFrame::createView(...) setting
     // various values such as setScrollBarModes(...) for example.  An ASSERT is
     // triggered when a view is layout before being attached to a frame().
     if (!frame().view())
         return;
@@ skipping 121 matching lines @@
         || (renderView && renderView->needsLayout())
         || isSubtreeLayout();
 }
 
 void FrameView::setNeedsLayout()
 {
     if (RenderView* renderView = this->renderView())
         renderView->setNeedsLayout();
 }
 
+void FrameView::setNeedsResizeLayout()
+{
+    if (RenderView* renderView = this->renderView()) {
+        if (m_firstLayout || m_frame->document()->printing())
+            renderView->setNeedsLayout();
+        else
+            renderView->setNeedsResizeLayout();
+    }
+}
+
 bool FrameView::isTransparent() const
 {
     return m_isTransparent;
 }
 
 void FrameView::setTransparent(bool isTransparent)
 {
     m_isTransparent = isTransparent;
     DisableCompositingQueryAsserts disabler;
     if (renderView() && renderView()->layer()->hasCompositedLayerMapping())
@@ skipping 1318 matching lines @@
 void FrameView::willRemoveScrollbar(Scrollbar* scrollbar, ScrollbarOrientation orientation)
 {
     ScrollableArea::willRemoveScrollbar(scrollbar, orientation);
     if (AXObjectCache* cache = axObjectCache()) {
         cache->remove(scrollbar);
         cache->handleScrollbarUpdate(this);
     }
 }
 
 } // namespace WebCore