Chromium compositor change implementing page-scale driven pinch-zoom.

cc/CCLayerImpl.h

Index: cc/CCLayerImpl.h
===================================================================
--- cc/CCLayerImpl.h	(revision 156389)
+++ cc/CCLayerImpl.h	(working copy)
@@ -174,13 +174,20 @@
     const FloatSize& scrollDelta() const { return m_scrollDelta; }
     void setScrollDelta(const FloatSize&);
 
+    const FloatSize& localOffset() const { return m_localOffset; }
+    void setLocalOffset(const FloatSize&);
+
     float pageScaleDelta() const { return m_pageScaleDelta; }
     void setPageScaleDelta(float);
 
+    float pageScaleFactor() const { return m_pageScaleFactor; }
+    void setPageScaleFactor(float scale) { m_pageScaleFactor = scale; }
+
     const IntSize& sentScrollDelta() const { return m_sentScrollDelta; }
     void setSentScrollDelta(const IntSize& sentScrollDelta) { m_sentScrollDelta = sentScrollDelta; }
 
-    void scrollBy(const FloatSize& scroll);
+    // Returns the delta of the scroll that was outside of the bounds of the initial scroll
+    FloatSize scrollBy(const FloatSize& scroll);
 
     bool scrollable() const { return m_scrollable; }
     void setScrollable(bool scrollable) { m_scrollable = scrollable; }
@@ -333,6 +340,8 @@
     IntSize m_sentScrollDelta;
     IntSize m_maxScrollPosition;
     float m_pageScaleDelta;
+    float m_pageScaleFactor;
+    FloatSize m_localOffset;
 
     // The layer whose coordinate space this layer draws into. This can be
     // either the same layer (m_renderTarget == this) or an ancestor of this