Only do aggressive metro viewer termination in tests

ash/test/test_metro_viewer_process_host.h

Index: ash/test/test_metro_viewer_process_host.h
diff --git a/ash/test/test_metro_viewer_process_host.h b/ash/test/test_metro_viewer_process_host.h
index f04ff0f0f3f902dbac355eebd8bc1d866c7e8fa6..cf7dcd0062b25f886c27f74695034cad9067fe9d 100644
--- a/ash/test/test_metro_viewer_process_host.h
+++ b/ash/test/test_metro_viewer_process_host.h
@@ -20,6 +20,10 @@ class TestMetroViewerProcessHost : public win8::MetroViewerProcessHost {
 
   bool closed_unexpectedly() { return closed_unexpectedly_; }
 
+  // Forcibly terminate the viewer. Used on completion of tests to ensure that
+  // it's gone (quickly) so that we can start the next test immediately.
+  void TerminateViewer();
+
  private:
   // win8::MetroViewerProcessHost implementation
   virtual void OnChannelError() OVERRIDE;