Hold RendererGL objects with a shared_ptr. To support both virtualized and unvirtualized contexts, the RendererGL object represents the native context. Update ContexGL and the various DisplayGLs to hold RendererGL with a shared_ptr so that deletion of the renderer happens at the correct time. Update RendererGL to take ownership of FunctionsGL. BUG=angleproject:2464 Change-Id: Id040a8053973d73936c0a7ff0ab5edb1a3f16dc6 Reviewed-on: https://chromium-review.googlesource.com/1085851 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Geoff Lang <geofflang@chromium.org>