- Validated by running:
	-functional_texture_specification_basic_copytexsubimage2d_*
	-functional_texture_specification_basic_copyteximage2d_*

With the flip flag enabled.

Bug: angleproject:2673
Change-Id: I5a3041af79f9316256b0650ab7e3fd0e086e46e3
Reviewed-on: https://chromium-review.googlesource.com/1129820
Commit-Queue: Luc Ferron <lucferron@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>