Disable MediaSourceTest.Playback_VideoOnly_WebM on Android Vulkan

MediaSourceTest.Playback_VideoOnly_WebM has begun flaking, up to 10% now.
I'm disabling it on vulkan_content_browsertests until the root cause can be addressed.

Also updating the bug id in the filter file to the unified bug covering this form of failure.

TBR=ynovikov@chromium.org
TEST=MediaSourceTest.Playback_VideoOnly_WebM
vulkan_content_browsertests
Bug: 985387

Change-Id: Ibac1705e890aeeccac01fbf671346567d562483b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1928058Reviewed-by: Jonathan Ross <jonross@chromium.org>
Commit-Queue: Jonathan Ross <jonross@chromium.org>
Cr-Commit-Position: refs/heads/master@{#717692}

testing/buildbot/filters/gpu.skiarenderer_vulkan_content_browsertests.filter

-# MediaBrowserTest error during playback. https://crbug.com/963266
+# MediaBrowserTest error during playback. https://crbug.com/985387
 -DevToolsVideoConsumerTest.SetMinAndMaxFramesChangesDimensions
 -File/MediaTest.VideoBearMp4/0
 -File/MediaTest.VideoTulipWebm/0
@@ -6,6 +6,7 @@
 -Http/MediaTest.VideoBearMp4/0
 -Http/MediaTest.VideoBearSilentMp4/0
 -Http/MediaTest.VideoTulipWebm/0
+-MediaSourceTest.Playback_VideoOnly_WebM
 -MSE_*ClearKey/EncryptedMediaTest.ConfigChangeVideo_ClearToClear/0
 -MSE_*ClearKey/EncryptedMediaTest.ConfigChangeVideo_ClearToEncrypted/0
 -MSE_*ClearKey/EncryptedMediaTest.ConfigChangeVideo_EncryptedToEncrypted/0