cc: Invalidate the full tiled layer when contents scale changes.

cc/contents_scaling_layer.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/contents_scaling_layer.h"
 #include "ui/gfx/size_conversions.h"
 
 namespace cc {
 
 gfx::Size ContentsScalingLayer::computeContentBoundsForScale(float scaleX, float scaleY) const {
   return gfx::ToCeiledSize(gfx::ScaleSize(bounds(), scaleX, scaleY));
 }
 
-ContentsScalingLayer::ContentsScalingLayer() {
+ContentsScalingLayer::ContentsScalingLayer()
+    : last_update_contents_scale_x_(0.f)
+    , last_update_contents_scale_y_(0.f)
+ {
 }
 
 ContentsScalingLayer::~ContentsScalingLayer() {
 }
 
 void ContentsScalingLayer::calculateContentsScale(
     float ideal_contents_scale,
     float* contents_scale_x,
     float* contents_scale_y,
     gfx::Size* content_bounds) {
   *contents_scale_x = ideal_contents_scale;
   *contents_scale_y = ideal_contents_scale;
   *content_bounds = computeContentBoundsForScale(
       ideal_contents_scale,
       ideal_contents_scale);
 }
 
 void ContentsScalingLayer::didUpdateBounds() {
   drawProperties().content_bounds = computeContentBoundsForScale(
       contentsScaleX(),
       contentsScaleY());
 }
 
+void ContentsScalingLayer::update(
+    ResourceUpdateQueue& queue,
+    const OcclusionTracker* occlusion,
+    RenderingStats& stats) {
+  if (drawProperties().contents_scale_x == last_update_contents_scale_x_ &&
+      drawProperties().contents_scale_y == last_update_contents_scale_y_)
+    return;
+  
+  last_update_contents_scale_x_ = drawProperties().contents_scale_x;
+  last_update_contents_scale_y_ = drawProperties().contents_scale_y;
+  // Invalidate the whole layer if scale changed.
+  setNeedsDisplayRect(gfx::Rect(bounds()));
+}
+
 }  // namespace cc