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

cc/resources/resource_pool.h

 // 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.
 
 #ifndef CC_RESOURCES_RESOURCE_POOL_H_
 #define CC_RESOURCES_RESOURCE_POOL_H_
 
 #include <list>
 
 #include "base/memory/scoped_ptr.h"
 #include "cc/base/cc_export.h"
 #include "cc/output/renderer.h"
 #include "cc/resources/resource.h"
 
 namespace cc {
 class ResourceProvider;
 
 class CC_EXPORT ResourcePool {
  public:
   class CC_EXPORT Resource : public cc::Resource {
    public:
     Resource(ResourceProvider* resource_provider,
-             const gfx::Size& size,
+             gfx::Size size,
              GLenum format);
     ~Resource();
 
    private:
     ResourceProvider* resource_provider_;
 
     DISALLOW_COPY_AND_ASSIGN(Resource);
   };
 
   static scoped_ptr<ResourcePool> Create(ResourceProvider* resource_provider) {
     return make_scoped_ptr(new ResourcePool(resource_provider));
   }
 
   virtual ~ResourcePool();
 
   ResourceProvider* resource_provider() { return resource_provider_; }
 
-  scoped_ptr<ResourcePool::Resource> AcquireResource(
-      const gfx::Size&, GLenum format);
+  scoped_ptr<ResourcePool::Resource> AcquireResource(gfx::Size size,
+                                                     GLenum format);
   void ReleaseResource(scoped_ptr<ResourcePool::Resource>);
 
   void SetMaxMemoryUsageBytes(
       size_t max_memory_usage_bytes,
       size_t max_unused_memory_usage_bytes);
 
  protected:
   explicit ResourcePool(ResourceProvider* resource_provider);
 
   bool MemoryUsageTooHigh();
 
  private:
   ResourceProvider* resource_provider_;
   size_t max_memory_usage_bytes_;
   size_t max_unused_memory_usage_bytes_;
   size_t memory_usage_bytes_;
   size_t unused_memory_usage_bytes_;
 
   typedef std::list<Resource*> ResourceList;
   ResourceList resources_;
 
   DISALLOW_COPY_AND_ASSIGN(ResourcePool);
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_RESOURCE_POOL_H_