This exposes previously enabled functionality. Also update the format
support check to be:

supported: GLES3 || texture extension
renderable: supported && color buffer extension
filterable: filtering extension

(Note: we silently support float rendering in ES2)

Re-land with suppression for newly exposed failing test.

BUG=angleproject:445

Change-Id: I4e46699e6b0c2ec8a7d8b36f1f598af1ec6420bc
Reviewed-on: https://chromium-review.googlesource.com/318931Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>