Use gpu::Mailbox in IPCs instead of std::string

cc/texture_layer_unittest.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/texture_layer.h"
 
 #include <string>
 
 #include "base/callback.h"
 #include "cc/layer_tree_host.h"
@@ skipping 275 matching lines @@
     {
     }
 
     // Make sure callback is received on main and doesn't block the impl thread.
     void releaseCallback(unsigned syncPoint) {
         EXPECT_EQ(true, proxy()->isMainThread());
         ++m_callbackCount;
     }
 
     void setMailbox(char mailbox_char) {
+        gpu::Mailbox name;
+        memset(name.name, mailbox_char, sizeof(name.name));
         TextureMailbox mailbox(
-            std::string(64, mailbox_char),
+            name,
             base::Bind(
                 &TextureLayerImplWithMailboxThreadedCallback::releaseCallback,
                 base::Unretained(this)));
         m_layer->setTextureMailbox(mailbox);
     }
 
     virtual void beginTest() OVERRIDE
     {
         gfx::Size bounds(100, 100);
         m_root = Layer::create();
@@ skipping 178 matching lines @@
     EXPECT_CALL(m_testData.m_mockCallback, Release(_, _)).Times(0);
     provider->deleteResource(id);
     Mock::VerifyAndClearExpectations(&m_testData.m_mockCallback);
     EXPECT_CALL(m_testData.m_mockCallback,
                 Release(m_testData.m_mailboxName1, _)).Times(1);
     provider->receiveFromParent(list);
 }
 
 }  // namespace
 }  // namespace cc