cc: Small cleanup to use an existing function instead of tilings search

cc/layers/picture_layer_impl.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/picture_layer_impl.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "base/debug/trace_event_argument.h"
@@ skipping 585 matching lines @@
 }
 
 const Region* PictureLayerImpl::GetInvalidation() {
   return &invalidation_;
 }
 
 const PictureLayerTiling* PictureLayerImpl::GetTwinTiling(
     const PictureLayerTiling* tiling) const {
   if (!twin_layer_)
     return NULL;
-  for (size_t i = 0; i < twin_layer_->tilings_->num_tilings(); ++i)
-    if (twin_layer_->tilings_->tiling_at(i)->contents_scale() ==
-        tiling->contents_scale())
-      return twin_layer_->tilings_->tiling_at(i);
-  return NULL;
+  return twin_layer_->tilings_->TilingAtScale(tiling->contents_scale());
 }
 
 size_t PictureLayerImpl::GetMaxTilesForInterestArea() const {
   return layer_tree_impl()->settings().max_tiles_for_interest_area;
 }
 
 float PictureLayerImpl::GetSkewportTargetTimeInSeconds() const {
   float skewport_target_time_in_frames =
       layer_tree_impl()->use_gpu_rasterization()
           ? kGpuSkewportTargetTimeInFrames
@@ skipping 1127 matching lines @@
       PictureLayerTilingSet::TilingRange tiling_range = CurrentTilingRange();
       size_t current_tiling_range_offset = current_tiling_ - tiling_range.start;
       return tiling_range.end - 1 - current_tiling_range_offset;
     }
   }
   NOTREACHED();
   return 0;
 }
 
 }  // namespace cc