Disable MediaTest.VideoBearWebm on valgrind ui_tests.
Disable MediaTest.VideoBearWebm on valgrind ui_tests.

On the CrOS UI (1) valgrind bot, this has been failing for the 5 days due to timeouts while running the test.

BUG=53825
TEST=None
Review URL: http://codereview.chromium.org/3219005

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@57850 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser