Temporarily remove ozone dependency for gl

The old implementation will result that the third party window system can't depend on ui/gl
because of cycling dependency. So temporarily remove ozone dependency for gl until we find a better method to resolve it.

This PR is corresponding to PR-246

BUG=240
I don't think this patch gets applied in the Chromium tree pointed by oz-wl's .DEPS.git file. The command `git show 528461056d2ef570281053dc5d9e0a5d8eb2e3f5:ui/gl/gl.gyp` shows a different snip of code than the one you are trying to remove here.