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

cc/CCLayerTreeHostCommon.cpp

Index: cc/CCLayerTreeHostCommon.cpp
===================================================================
--- cc/CCLayerTreeHostCommon.cpp	(revision 159486)
+++ cc/CCLayerTreeHostCommon.cpp	(working copy)
@@ -271,7 +271,7 @@
     //
 
     WebTransformationMatrix partialLayerOriginTransform = parentMatrix;
-    partialLayerOriginTransform.scale(scrollingLayer->pageScaleDelta());
+    partialLayerOriginTransform.multiply(scrollingLayer->implTransform());
 
     WebTransformationMatrix scrollCompensationForThisLayer = partialLayerOriginTransform; // Step 3
     scrollCompensationForThisLayer.translate(scrollingLayer->scrollDelta().width(), scrollingLayer->scrollDelta().height()); // Step 2
@@ -468,13 +468,13 @@
     float centerOffsetY = (0.5 - anchorPoint.y()) * bounds.height();
 
     WebTransformationMatrix layerLocalTransform;
-    // LT = S[pageScaleDelta]
-    layerLocalTransform.scale(layer->pageScaleDelta());
-    // LT = S[pageScaleDelta] * Tr[origin] * Tr[origin2anchor]
+    // LT = M[impl transformation]
+    layerLocalTransform.multiply(layer->implTransform());
+    // LT = M[impl transformation] * Tr[origin] * Tr[origin2anchor]
     layerLocalTransform.translate3d(position.x() + anchorPoint.x() * bounds.width(), position.y() + anchorPoint.y() * bounds.height(), layer->anchorPointZ());
-    // LT = S[pageScaleDelta] * Tr[origin] * Tr[origin2anchor] * M[layer]
+    // LT = M[impl transformation] * Tr[origin] * Tr[origin2anchor] * M[layer]
     layerLocalTransform.multiply(layer->transform());
-    // LT = S[pageScaleDelta] * Tr[origin] * Tr[origin2anchor] * M[layer] * Tr[anchor2center]
+    // LT = M[impl transformation] * Tr[origin] * Tr[origin2anchor] * M[layer] * Tr[anchor2center]
     layerLocalTransform.translate3d(centerOffsetX, centerOffsetY, -layer->anchorPointZ());
 
     WebTransformationMatrix combinedTransform = parentMatrix;