This involves cases of copying from a rotated default framebuffer.
Various adjustments are needed for where the source is and its
relationship to gl_FragCoord in the custom ImageCopy fragment
shaders.  Various tests are affected, including the following:

Test: angle_deqp_gles2_tests --gtest_filter=dEQP.GLES2/functional_texture_specification_basic_copy*teximage2d_*
Test: angle_deqp_gles3_tests --gtest_filter=dEQP.GLES3/functional_texture_specification_basic_copy*teximage2d_*
Bug: b/158245571
Bug: b/157933235
Change-Id: Id9ec56d849cd2268954dd82623a7632a10fb8e8f
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2248204Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>
Commit-Queue: Ian Elliott <ianelliott@google.com>