With the addition of EGL Image, the display extensions generated by
Renderer9 and Renderer11 become significantly different.  Instead of
generating them via getXSupport() methods, generate them inside the
renderers themselves.

BUG=angleproject:970

Change-Id: Ib3fffabcca3e3cdef13ef994aa0b06dba0f00362
Reviewed-on: https://chromium-review.googlesource.com/293271Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>