This paves the way for setting data on the TextureStorage directly instead of working through the Image objects. BUG=angle:741 Change-Id: I3be3d5f9b2e45707c1630b74ad3f4789e034c3fd Reviewed-on: https://chromium-review.googlesource.com/218311Reviewed-by: Geoff Lang <geofflang@chromium.org> Tested-by: Jamie Madill <jmadill@chromium.org>
