Pass references to BinComparator.

cc/resources/tile_manager.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/resources/tile_manager.h"
 
 #include <algorithm>
 #include <limits>
 #include <string>
 
@@ skipping 217 matching lines @@
   // memory and in worst case use on-demand raster when tiles
   // required for activation are OOM.
   if (!all_tiles_required_for_activation_have_memory_)
     return;
 
   client_->NotifyReadyToActivate();
 }
 
 class BinComparator {
  public:
-  bool operator()(const scoped_refptr<Tile> a,
-                  const scoped_refptr<Tile> b) const {
+  bool operator()(const scoped_refptr<Tile>& a,
+                  const scoped_refptr<Tile>& b) const {
     const ManagedTileState& ams = a->managed_state();
     const ManagedTileState& bms = b->managed_state();
 
     if (ams.visible_and_ready_to_draw != bms.visible_and_ready_to_draw)
       return ams.visible_and_ready_to_draw;
 
     if (ams.bin[HIGH_PRIORITY_BIN] != bms.bin[HIGH_PRIORITY_BIN])
       return ams.bin[HIGH_PRIORITY_BIN] < bms.bin[HIGH_PRIORITY_BIN];
 
     if (ams.bin[LOW_PRIORITY_BIN] != bms.bin[LOW_PRIORITY_BIN])
@@ skipping 576 matching lines @@
     tile_version.set_use_resource();
     tile_version.resource_ = resource.Pass();
   }
 
   FreeUnusedResourcesForTile(tile);
   if (tile->priority(ACTIVE_TREE).distance_to_visible_in_pixels == 0)
     did_initialize_visible_tile_ = true;
 }
 
 }  // namespace cc