Add mpeg for layouttests to pass.  The following media layout tests fail if mpeg (ie mpg) is not supported.
Add mpeg for layouttests to pass.  The following media layout tests fail if mpeg (ie mpg) is not supported.

  LayoutTests/media/video-source-add-src.html = FAIL
  LayoutTests/media/video-source-error.html = FAIL
  LayoutTests/media/video-source-type-params.html = FAIL
  LayoutTests/media/video-source-type.html = FAIL

Review URL: http://codereview.chromium.org/149241

git-svn-id: http://src.chromium.org/svn/trunk/src@20011 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 98fa338b9e6fd9e791b67bf50b7ed759c34de2ac
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser