[chromedriver] Remove chrome 28 from chromedriver test suite and add 31.
BUG=none
TBR=chrisgao

Review URL: https://codereview.chromium.org/24926003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225639 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225639