Ozone caca: Fix segfault during GPU initialization

After https://codereview.chromium.org/2270463002,
gl::init::GetAllowedGLImplementations assumes GetSurfaceFactoryOzone to
be non-null on the GPU side. The remaining Ozone platform violating
this assumption is addressed in this CL.

BUG=640613
R=rjkroege@chromium.org

Review-Url: https://codereview.chromium.org/2346433002
Cr-Commit-Position: refs/heads/master@{#418781}
1 file changed