Enable a ui test that plays video without audio stream...

chrome/browser/media_uitest.cc

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/basictypes.h"
 #include "base/file_path.h"
 #include "base/platform_thread.h"
 #include "base/string_util.h"
 #include "chrome/test/ui/ui_test.h"
 #include "net/base/net_util.h"
@@ skipping 29 matching lines @@
 
   void PlayAudio(const char* url) {
     PlayMedia("audio", url);
   }
 
   void PlayVideo(const char* url) {
     PlayMedia("video", url);
   }
 };
 
+// <video> and <audio> only works stably on Windows.
+#if defined(OS_WIN)
+
+// TODO(hclam): The following test is disabled because it contains audio and
+// this test doesn't work with audio device.
 TEST_F(MediaTest, DISABLED_VideoBearH264) {
   PlayVideo("bear.mp4");
 }
+
+TEST_F(MediaTest, VideoBearSilentTheora) {
+  PlayVideo("bear_silent.ogv");
+}
+
+#endif