Bug 1294420 - Skip tests that use h264 on WinXP. r=gerald

Fix permafail for mda on WinXP which has no h264

MozReview-Commit-ID: 35tlO5vPTLD

--HG--
extra : rebase_source : 4d0edc219f75bd2107a3828a4df6419d7449657a

dom/media/test/mochitest.ini

@@ -886,8 +886,11 @@ tags = webvtt
 [test_fragment_play.html]
 
 [test_background_video_suspend.html]
+skip-if = (os == 'win' && os_version == '5.1')
 tags = suspend
 [test_background_video_no_suspend_short_vid.html]
+skip-if = (os == 'win' && os_version == '5.1')
 tags = suspend
 [test_background_video_no_suspend_disabled.html]
+skip-if = (os == 'win' && os_version == '5.1')
 tags = suspend