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

chrome/browser/metro_viewer/chrome_metro_viewer_process_host_aurawin.cc

Index: chrome/browser/metro_viewer/chrome_metro_viewer_process_host_aurawin.cc
diff --git a/chrome/browser/metro_viewer/chrome_metro_viewer_process_host_aurawin.cc b/chrome/browser/metro_viewer/chrome_metro_viewer_process_host_aurawin.cc
index 268510ec1eb92b2ede603696c99338ebc6891c9d..7ba1f9c43df3ecaa6edf8f17bc5c43ee9dd2e025 100644
--- a/chrome/browser/metro_viewer/chrome_metro_viewer_process_host_aurawin.cc
+++ b/chrome/browser/metro_viewer/chrome_metro_viewer_process_host_aurawin.cc
@@ -57,12 +57,10 @@ void OpenURL(const GURL& url) {
 
 }  // namespace
 
-ChromeMetroViewerProcessHost::ChromeMetroViewerProcessHost(
-    const std::string& ipc_channel_name)
-        : MetroViewerProcessHost(
-              ipc_channel_name,
-              content::BrowserThread::GetMessageLoopProxyForThread(
-                  content::BrowserThread::IO)) {
+ChromeMetroViewerProcessHost::ChromeMetroViewerProcessHost()
+    : MetroViewerProcessHost(
+          content::BrowserThread::GetMessageLoopProxyForThread(
+              content::BrowserThread::IO)) {
   g_browser_process->AddRefModule();
 }