StructTraits optimizations

cc/ipc/transferable_resource_struct_traits.h

 // Copyright 2016 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_IPC_TRANSFERABLE_RESOURCE_STRUCT_TRAITS_H_
 #define CC_IPC_TRANSFERABLE_RESOURCE_STRUCT_TRAITS_H_
 
 #include "cc/ipc/transferable_resource.mojom.h"
 #include "cc/resources/transferable_resource.h"
 
@@ skipping 11 matching lines @@
   }
 
   static uint32_t filter(const cc::TransferableResource& resource) {
     return resource.filter;
   }
 
   static gfx::Size size(const cc::TransferableResource& resource) {
     return resource.size;
   }
 
-  static gpu::MailboxHolder mailbox_holder(
+  static const gpu::MailboxHolder& mailbox_holder(
       const cc::TransferableResource& resource) {
     return resource.mailbox_holder;
   }
 
   static bool read_lock_fences_enabled(
       const cc::TransferableResource& resource) {
     return resource.read_lock_fences_enabled;
   }
 
   static bool is_software(const cc::TransferableResource& resource) {
     return resource.is_software;
   }
 
   static int32_t gpu_memory_buffer_id(
       const cc::TransferableResource& resource) {
     return resource.gpu_memory_buffer_id.id;
   }
 
   static bool is_overlay_candidate(const cc::TransferableResource& resource) {
     return resource.is_overlay_candidate;
   }
 
   static bool Read(cc::mojom::TransferableResourceDataView data,
                    cc::TransferableResource* out) {
-    gfx::Size size;
-    gpu::MailboxHolder holder;
-    if (!data.ReadSize(&size) || !data.ReadMailboxHolder(&holder))
+    if (!data.ReadSize(&out->size) ||
+        !data.ReadMailboxHolder(&out->mailbox_holder))
       return false;
     out->id = data.id();
     out->format = static_cast<cc::ResourceFormat>(data.format());
     out->filter = data.filter();
-    out->size = size;
-    out->mailbox_holder = holder;
     out->read_lock_fences_enabled = data.read_lock_fences_enabled();
     out->is_software = data.is_software();
     out->gpu_memory_buffer_id.id = data.gpu_memory_buffer_id();
     out->is_overlay_candidate = data.is_overlay_candidate();
     return true;
   }
 };
 
 }  // namespace mojo
 
 #endif  // CC_IPC_TRANSFERABLE_RESOURCE_STRUCT_TRAITS_H_