Fix ApproximatelyEqual for transforms

cc/layers/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/layers/contents_scaling_layer.h"
+#include "cc/trees/layer_tree_host.h"
 #include "ui/gfx/geometry/size_conversions.h"
 
 namespace cc {
 
 gfx::Size ContentsScalingLayer::ComputeContentBoundsForScale(
     float scale_x,
     float scale_y) const {
   return gfx::ToCeiledSize(gfx::ScaleSize(bounds(), scale_x, scale_y));
 }
 
 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) {
+  float old_contents_scale_x = *contents_scale_x;
+  float old_contents_scale_y = *contents_scale_y;
+  gfx::Size old_content_bounds = *content_bounds;
   *contents_scale_x = ideal_contents_scale;
   *contents_scale_y = ideal_contents_scale;
   *content_bounds = ComputeContentBoundsForScale(
       ideal_contents_scale,
       ideal_contents_scale);
+
+  if (!layer_tree_host())
+    return;
+
+  if (old_contents_scale_x != *contents_scale_x ||
+      old_contents_scale_y != *contents_scale_y ||
+      old_content_bounds != *content_bounds) {
+    layer_tree_host()->property_trees()->needs_rebuild = true;
+  }
 }
 
 bool ContentsScalingLayer::Update(ResourceUpdateQueue* queue,
                                   const OcclusionTracker<Layer>* occlusion) {
   bool updated = Layer::Update(queue, occlusion);
 
   if (draw_properties().contents_scale_x == last_update_contents_scale_x_ &&
       draw_properties().contents_scale_y == last_update_contents_scale_y_)
     return updated;
 
   last_update_contents_scale_x_ = draw_properties().contents_scale_x;
   last_update_contents_scale_y_ = draw_properties().contents_scale_y;
   // Invalidate the whole layer if scale changed.
   SetNeedsDisplayRect(gfx::Rect(paint_properties().bounds));
   return updated;
 }
 
 }  // namespace cc