Only do aggressive metro viewer termination in tests

ash/test/ash_test_base.cc

Index: ash/test/ash_test_base.cc
diff --git a/ash/test/ash_test_base.cc b/ash/test/ash_test_base.cc
index 166e2b7d007df4a1aebf69a5e40342c9c753bfae..912c1e676ccadea7efa877f27ecb2567b83dae5a 100644
--- a/ash/test/ash_test_base.cc
+++ b/ash/test/ash_test_base.cc
@@ -176,15 +176,8 @@ void AshTestBase::TearDown() {
 #if defined(OS_WIN)
   ui::test::SetUsePopupAsRootWindowForTest(false);
   // Kill the viewer process if we spun one up.
+  metro_viewer_host_->TerminateViewer();
   metro_viewer_host_.reset();
-
-  // Clean up any dangling viewer processes as the metro APIs sometimes leave
-  // zombies behind. A default browser process in metro will have the
-  // following command line arg so use that to avoid killing all processes named
-  // win8::test::kDefaultTestExePath.
-  const wchar_t kViewerProcessArgument[] = L"DefaultBrowserServer";
-  base::KillAllNamedProcessesWithArgument(win8::test::kDefaultTestExePath,
-                                          kViewerProcessArgument);
 #endif
 
   event_generator_.reset();