StructTraits optimizations

cc/ipc/selection_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_SELECTION_STRUCT_TRAITS_H_
 #define CC_IPC_SELECTION_STRUCT_TRAITS_H_
 
 #include "cc/input/selection.h"
 #include "cc/ipc/selection.mojom.h"
 
 namespace mojo {
 
 template <>
 struct StructTraits<cc::mojom::Selection, cc::Selection<gfx::SelectionBound>> {
-  static gfx::SelectionBound start(
+  static const gfx::SelectionBound& start(
       const cc::Selection<gfx::SelectionBound>& selection) {
     return selection.start;
   }
 
-  static gfx::SelectionBound end(
+  static const gfx::SelectionBound& end(
       const cc::Selection<gfx::SelectionBound>& selection) {
     return selection.end;
   }
 
   static bool is_editable(const cc::Selection<gfx::SelectionBound>& selection) {
     return selection.is_editable;
   }
 
   static bool is_empty_text_form_control(
       const cc::Selection<gfx::SelectionBound>& selection) {
     return selection.is_empty_text_form_control;
   }
 
   static bool Read(cc::mojom::SelectionDataView data,
                    cc::Selection<gfx::SelectionBound>* out) {
     if (!data.ReadStart(&out->start) || !data.ReadEnd(&out->end))
       return false;
 
     out->is_editable = data.is_editable();
     out->is_empty_text_form_control = data.is_empty_text_form_control();
     return true;
   }
 };
 
 }  // namespace mojo
 
 #endif  // CC_IPC_SELECTION_STRUCT_TRAITS_H_