Refactor fixed layout mode

Source/core/page/FrameView.h

Index: Source/core/page/FrameView.h
diff --git a/Source/core/page/FrameView.h b/Source/core/page/FrameView.h
index 697459c8412a12beda8b296580ba9f960fa32398..b522cd0c37cc5c48dd871137a05ea6f3e9b77a49 100644
--- a/Source/core/page/FrameView.h
+++ b/Source/core/page/FrameView.h
@@ -108,6 +108,10 @@ public:
     void setNeedsLayout();
     void setViewportConstrainedObjectsNeedLayout();
 
+    // Methods for getting/setting the size Blink should use to layout the contents.
+    IntSize layoutSize(IncludeScrollbarsInRect = ExcludeScrollbars) const;
+    void setLayoutSize(const IntSize&);
+
     bool needsFullRepaint() const { return m_doFullRepaint; }
 
     void serviceScriptedAnimations(double monotonicAnimationStartTime);
@@ -349,6 +353,7 @@ private:
     void reset();
     void init();
 
+    virtual void frameRectsChanged();
     virtual bool isFrameView() const OVERRIDE { return true; }
 
     friend class RenderWidget;
@@ -374,7 +379,7 @@ private:
 
     virtual void repaintContentRectangle(const IntRect&);
     virtual void contentsResized() OVERRIDE;
-    virtual void visibleContentsResized();
+    virtual void scrollbarExistenceDidChange();
 
     // Override ScrollView methods to do point conversion via renderers, in order to
     // take transforms into account.
@@ -538,6 +543,7 @@ private:
     float m_visibleContentScaleFactor;
 
     PartialLayoutState m_partialLayout;
+    IntSize m_layoutSize;
 };
 
 inline void FrameView::incrementVisuallyNonEmptyCharacterCount(unsigned count)