Make the browser->metro_viewer IPC channel name a constant instead of hardcoding it in a few places…

ash/test/ash_test_base.cc

 // Copyright (c) 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 "ash/test/ash_test_base.h"
 
 #include <string>
 #include <vector>
 
 #include "ash/ash_switches.h"
@@ skipping 106 matching lines @@
 #if defined(OS_WIN)
   if (base::win::GetVersion() >= base::win::VERSION_WIN8 &&
       !CommandLine::ForCurrentProcess()->HasSwitch(
           ash::switches::kForceAshToDesktop)) {
     ipc_thread_.reset(new base::Thread("test_metro_viewer_ipc_thread"));
     base::Thread::Options options;
     options.message_loop_type = base::MessageLoop::TYPE_IO;
     ipc_thread_->StartWithOptions(options);
 
     metro_viewer_host_.reset(
-        new TestMetroViewerProcessHost("viewer",
-                                       ipc_thread_->message_loop_proxy()));
+        new TestMetroViewerProcessHost(ipc_thread_->message_loop_proxy()));
     CHECK(metro_viewer_host_->LaunchViewerAndWaitForConnection(
         win8::test::kDefaultTestAppUserModelId));
     aura::RemoteRootWindowHostWin* root_window_host =
         aura::RemoteRootWindowHostWin::Instance();
     CHECK(root_window_host != NULL);
   }
 #endif
 }
 
 void AshTestBase::TearDown() {
@@ skipping 133 matching lines @@
       SetHasActiveUser(user_logged_in);
 }
 
 void AshTestBase::SetCanLockScreen(bool can_lock_screen) {
   ash_test_helper_->test_shell_delegate()->test_session_state_delegate()->
       SetCanLockScreen(can_lock_screen);
 }
 
 }  // namespace test
 }  // namespace ash