Rasterize at maximum scale for scale animations on CPU-rasterized layers

cc/layers/painted_scrollbar_layer.cc

 // Copyright 2013 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/painted_scrollbar_layer.h"
 
 #include "base/auto_reset.h"
 #include "base/basictypes.h"
 #include "base/debug/trace_event.h"
 #include "cc/layers/painted_scrollbar_layer_impl.h"
@@ skipping 82 matching lines @@
     else
       return (MaxTextureSize() - 1) / static_cast<float>(bounds().height());
   }
   return scale;
 }
 
 void PaintedScrollbarLayer::CalculateContentsScale(
     float ideal_contents_scale,
     float device_scale_factor,
     float page_scale_factor,
+    float maximum_animation_contents_scale,
     bool animating_transform_to_screen,
     float* contents_scale_x,
     float* contents_scale_y,
     gfx::Size* content_bounds) {
   ContentsScalingLayer::CalculateContentsScale(
       ClampScaleToMaxTextureSize(ideal_contents_scale),
       device_scale_factor,
       page_scale_factor,
+      maximum_animation_contents_scale,
       animating_transform_to_screen,
       contents_scale_x,
       contents_scale_y,
       content_bounds);
 }
 
 void PaintedScrollbarLayer::PushPropertiesTo(LayerImpl* layer) {
   ContentsScalingLayer::PushPropertiesTo(layer);
 
   PushScrollClipPropertiesTo(layer);
@@ skipping 148 matching lines @@
 
   scrollbar_->PaintPart(&skcanvas, part, layer_rect);
   // Make sure that the pixels are no longer mutable to unavoid unnecessary
   // allocation and copying.
   skbitmap.setImmutable();
 
   return UIResourceBitmap(skbitmap);
 }
 
 }  // namespace cc