cc: Don't pass simple well-defined classes by reference.

cc/resources/picture_layer_tiling.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/picture_layer_tiling.h"
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/debug/trace_event.h"
@@ skipping 49 matching lines @@
   gfx::Rect tile_rect = tiling_data_.TileBoundsWithBorder(i, j);
   tile_rect.set_size(tiling_data_.max_texture_size());
   TileMapKey key(i, j);
   DCHECK(tiles_.find(key) == tiles_.end());
   scoped_refptr<Tile> tile = client_->CreateTile(this, tile_rect);
   if (tile)
     tiles_[key] = tile;
 }
 
 Region PictureLayerTiling::OpaqueRegionInContentRect(
-    const gfx::Rect& content_rect) const {
+    gfx::Rect content_rect) const {
   Region opaque_region;
   // TODO(enne): implement me
   return opaque_region;
 }
 
 void PictureLayerTiling::SetLayerBounds(gfx::Size layer_bounds) {
   if (layer_bounds_ == layer_bounds)
     return;
 
   gfx::Size old_layer_bounds = layer_bounds_;
@@ skipping 572 matching lines @@
 
     // If our delta is less then our event distance, we're done.
     if (delta < event.distance)
       break;
   }
 
   return gfx::Rect(origin_x, origin_y, width, height);
 }
 
 }  // namespace cc