Plumb preferred raster scale for background images from Blink to cc layers.

cc/blink/web_layer_impl.cc

 // Copyright 2014 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/blink/web_layer_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <utility>
@@ skipping 456 matching lines @@
 }
 
 void WebLayerImpl::SetContentsOpaqueIsFixed(bool fixed) {
   contents_opaque_is_fixed_ = fixed;
 }
 
 void WebLayerImpl::setHasWillChangeTransformHint(bool has_will_change) {
   layer_->SetHasWillChangeTransformHint(has_will_change);
 }
 
+void WebLayerImpl::setPreferredRasterScale(float raster_scale) {
+  layer_->SetPreferredRasterScale(raster_scale);
+}
+
+void WebLayerImpl::clearPreferredRasterScale() {
+  layer_->ClearPreferredRasterScale();
+}
+
 }  // namespace cc_blink