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

cc/CCLayerImpl.cpp

Index: cc/CCLayerImpl.cpp
===================================================================
--- cc/CCLayerImpl.cpp	(revision 156389)
+++ cc/CCLayerImpl.cpp	(working copy)
@@ -48,6 +48,7 @@
     , m_isContainerForFixedPositionLayers(false)
     , m_fixedToContainerLayer(false)
     , m_pageScaleDelta(1)
+    , m_pageScaleFactor(1)
     , m_renderTarget(0)
     , m_drawDepth(0)
     , m_drawOpacity(0)
@@ -159,20 +160,23 @@
     return 0;
 }
 
-void CCLayerImpl::scrollBy(const FloatSize& scroll)
+FloatSize CCLayerImpl::scrollBy(const FloatSize& scroll)
 {
     IntSize minDelta = -toSize(m_scrollPosition);
     IntSize maxDelta = m_maxScrollPosition - toSize(m_scrollPosition);
     // Clamp newDelta so that position + delta stays within scroll bounds.
     FloatSize newDelta = (m_scrollDelta + scroll).expandedTo(minDelta).shrunkTo(maxDelta);
+    FloatSize unscrolled = m_scrollDelta + scroll - newDelta;
 
     if (m_scrollDelta == newDelta)
-        return;
+        return unscrolled;
 
     m_scrollDelta = newDelta;
     if (m_scrollbarAnimationController)
         m_scrollbarAnimationController->updateScrollOffset(this);
     noteLayerPropertyChangedForSubtree();
+
+    return unscrolled;
 }
 
 CCInputHandlerClient::ScrollStatus CCLayerImpl::tryScroll(const IntPoint& viewportPoint, CCInputHandlerClient::ScrollInputType type) const
@@ -558,6 +562,15 @@
     noteLayerPropertyChangedForSubtree();
 }
 
+void CCLayerImpl::setLocalOffset(const FloatSize& offset)
+{
+    if (m_localOffset == offset)
+        return;
+
+    m_localOffset = offset;
+    noteLayerPropertyChangedForSubtree();
+}
+
 void CCLayerImpl::setPageScaleDelta(float pageScaleDelta)
 {
     if (m_pageScaleDelta == pageScaleDelta)