Revert of [#7] Pass gfx structs by const ref (gfx::Size)

cc/trees/layer_tree_host_impl.h

 // Copyright 2011 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.
 
 #ifndef CC_TREES_LAYER_TREE_HOST_IMPL_H_
 #define CC_TREES_LAYER_TREE_HOST_IMPL_H_
 
 #include <list>
 #include <set>
 #include <string>
@@ skipping 279 matching lines @@
   bool visible() const { return visible_; }
 
   void SetNeedsCommit() { client_->SetNeedsCommitOnImplThread(); }
   void SetNeedsRedraw();
 
   ManagedMemoryPolicy ActualManagedMemoryPolicy() const;
 
   size_t memory_allocation_limit_bytes() const;
   int memory_allocation_priority_cutoff() const;
 
-  void SetViewportSize(const gfx::Size& device_viewport_size);
+  void SetViewportSize(gfx::Size device_viewport_size);
 
   void SetOverdrawBottomHeight(float overdraw_bottom_height);
   float overdraw_bottom_height() const { return overdraw_bottom_height_; }
 
   void SetOverhangUIResource(UIResourceId overhang_ui_resource_id,
-                             const gfx::Size& overhang_ui_resource_size);
+                             gfx::Size overhang_ui_resource_size);
 
   void SetDeviceScaleFactor(float device_scale_factor);
   float device_scale_factor() const { return device_scale_factor_; }
 
   const gfx::Transform& DrawTransform() const;
 
   scoped_ptr<ScrollAndScaleSet> ProcessScrollDeltas();
 
   bool needs_animate_layers() const {
     return !animation_registrar_->active_animation_controllers().empty();
@@ skipping 335 matching lines @@
   int id_;
 
   std::set<SwapPromiseMonitor*> swap_promise_monitor_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_IMPL_H_