Disable ComboboxTest.ContentWidth which broke ASan Linux

BUG=341042
TBR=hajimehoshi@chromium.org

Review URL: https://codereview.chromium.org/153763003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249003 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249003