Add a few more gfx::Animation timing functions as per request from mclement@

BUG=334428
TEST=None

Review URL: https://codereview.chromium.org/156873005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250160 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250160