Optimize layout/repaint on FrameView resize

Source/core/frame/FrameView.cpp

Index: Source/core/frame/FrameView.cpp
diff --git a/Source/core/frame/FrameView.cpp b/Source/core/frame/FrameView.cpp
index 95f79cbc724c033eeb430f97c5e0db39788b65c4..50d650980e1332482f835e7d77dacf887179f1bf 100644
--- a/Source/core/frame/FrameView.cpp
+++ b/Source/core/frame/FrameView.cpp
@@ -942,7 +942,11 @@ void FrameView::layout(bool allowSubtree)
             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;
@@ -1746,7 +1750,7 @@ void FrameView::repaintContentRectangle(const IntRect& r)
 void FrameView::contentsResized()
 {
     ScrollView::contentsResized();
-    setNeedsLayout();
+    setNeedsResizeLayout();
 }
 
 void FrameView::scrollbarExistenceDidChange()
@@ -1888,6 +1892,16 @@ void FrameView::setNeedsLayout()
         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;