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

ash/test/test_metro_viewer_process_host.cc

Index: ash/test/test_metro_viewer_process_host.cc
diff --git a/ash/test/test_metro_viewer_process_host.cc b/ash/test/test_metro_viewer_process_host.cc
index 3819d3541158796499ea3556e8679acc80e0e1d2..a788da9f323ea1191bfee2c3e88ca35fab339336 100644
--- a/ash/test/test_metro_viewer_process_host.cc
+++ b/ash/test/test_metro_viewer_process_host.cc
@@ -4,30 +4,18 @@
 
 #include "ash/test/test_metro_viewer_process_host.h"
 
-#include <shellapi.h>
-#include <shlobj.h>
-
-#include "base/command_line.h"
-#include "base/file_util.h"
-#include "base/files/file_path.h"
-#include "base/strings/string16.h"
-#include "base/time.h"
-#include "base/win/scoped_com_initializer.h"
-#include "base/win/scoped_comptr.h"
-#include "ipc/ipc_channel_proxy.h"
-#include "ipc/ipc_message_macros.h"
+#include <windef.h>
+
+#include "base/logging.h"
 #include "ui/aura/remote_root_window_host_win.h"
-#include "ui/metro_viewer/metro_viewer_messages.h"
 #include "ui/surface/accelerated_surface_win.h"
 
 namespace ash {
 namespace test {
 
 TestMetroViewerProcessHost::TestMetroViewerProcessHost(
-    const std::string& ipc_channel_name,
     base::SingleThreadTaskRunner* ipc_task_runner)
-        : MetroViewerProcessHost(ipc_channel_name, ipc_task_runner),
-          closed_unexpectedly_(false) {
+        : MetroViewerProcessHost(ipc_task_runner), closed_unexpectedly_(false) {
 }
 
 TestMetroViewerProcessHost::~TestMetroViewerProcessHost() {
@@ -43,7 +31,7 @@ void TestMetroViewerProcessHost::OnSetTargetSurface(
   DLOG(INFO) << __FUNCTION__ << ", target_surface = " << target_surface;
   HWND hwnd = reinterpret_cast<HWND>(target_surface);
 
-  backing_surface.reset(new AcceleratedSurface(hwnd));
+  backing_surface_.reset(new AcceleratedSurface(hwnd));
 
   scoped_refptr<AcceleratedPresenter> any_window =
       AcceleratedPresenter::GetForWindow(NULL);