Have browser process shutdown metro viewer on Metro -> Metro restart.

chrome/browser/browser_process_platform_part_aurawin.h

Index: chrome/browser/browser_process_platform_part_aurawin.h
diff --git a/chrome/browser/browser_process_platform_part_aurawin.h b/chrome/browser/browser_process_platform_part_aurawin.h
index 8c2b96d9a2266510a72208723579ebbe76ee994d..4d202dd75e72334afd54a1bbd25447295d4af428 100644
--- a/chrome/browser/browser_process_platform_part_aurawin.h
+++ b/chrome/browser/browser_process_platform_part_aurawin.h
@@ -8,10 +8,13 @@
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "chrome/browser/browser_process_platform_part_base.h"
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
 
 class ChromeMetroViewerProcessHost;
 
-class BrowserProcessPlatformPart : public BrowserProcessPlatformPartBase {
+class BrowserProcessPlatformPart : public BrowserProcessPlatformPartBase,
+                                   public content::NotificationObserver {
  public:
   BrowserProcessPlatformPart();
   virtual ~BrowserProcessPlatformPart();
@@ -23,11 +26,18 @@ class BrowserProcessPlatformPart : public BrowserProcessPlatformPartBase {
   virtual void PlatformSpecificCommandLineProcessing(
       const CommandLine& command_line) OVERRIDE;
 
+  // content::NotificationObserver method:
+  virtual void Observe(int type,
+                       const content::NotificationSource& source,
+                       const content::NotificationDetails& details) OVERRIDE;
+
  private:
   // Hosts the channel for the Windows 8 metro viewer process which runs in
   // the ASH environment.
   scoped_ptr<ChromeMetroViewerProcessHost> metro_viewer_process_host_;
 
+  content::NotificationRegistrar registrar_;
+
   DISALLOW_COPY_AND_ASSIGN(BrowserProcessPlatformPart);
 };