Revert of cc: Disable "activate to low res" optimization

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/time/time.h"
@@ skipping 745 matching lines @@
   // them and only allow activating to high res tiles, since tiles on each layer
   // will be in different places on screen.
   if (!twin_high_res || !twin_low_res ||
       twin_layer_->layer_tree_impl()->RequiresHighResToDraw() ||
       draw_properties().screen_space_transform !=
           twin_layer_->draw_properties().screen_space_transform) {
     twin_high_res = NULL;
     twin_low_res = NULL;
   }
 
-  // TODO(enne): temporarily disable this optimization: http://crbug.com/335289
-  twin_high_res = NULL;
-  twin_low_res = NULL;
-
   // As a second pass, mark as required any visible high res tiles not filled in
   // by acceptable non-ideal tiles from the first pass.
   if (MarkVisibleTilesAsRequired(
       high_res, twin_high_res, contents_scale_x(), rect, missing_region)) {
     // As an optional third pass, if a high res tile was skipped because its
     // twin was also missing, then fall back to mark low res tiles as required
     // in case the active twin is substituting those for missing high res
     // content.
     MarkVisibleTilesAsRequired(
         low_res, twin_low_res, contents_scale_x(), rect, missing_region);
@@ skipping 456 matching lines @@
 size_t PictureLayerImpl::GPUMemoryUsageInBytes() const {
   const_cast<PictureLayerImpl*>(this)->DoPostCommitInitializationIfNeeded();
   return tilings_->GPUMemoryUsageInBytes();
 }
 
 void PictureLayerImpl::RunMicroBenchmark(MicroBenchmarkImpl* benchmark) {
   benchmark->RunOnLayer(this);
 }
 
 }  // namespace cc