Add support for GL_REPEAT in software compositor.

This is used to draw the overscroll gutters on Mac.

BUG=286038

Review URL: https://codereview.chromium.org/53183002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236201 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236201