This reverts commit 17d27031.

Reason for revert:
 - New test fails on NVIDIA and AMD on Windows when using the backbuffer FAST_PATH.
 - SetUp code ASSERT_GL_NO_ERROR (line 269) but a GL error happens on all Windows and Linux Intel OpenGL.

Original change's description:
> Fix BlitFramebuffer validation for BGRA sources and targets.
> 
> It is legal to blit between GL_RGBA8 and GL_BGRA8 sources and
> destinations when resolving multisampled renderbuffers. Expand
> BlitFramebuffer's validation to handle this case.
> 
> Work around a bug in macOS' OpenGL driver querying the number of
> samples for GL_BGRA8.
> 
> Query GL_MAX_VERTEX_OUTPUT_COMPONENTS on the Core Profile to work
> around an error generated on macOS when querying
> GL_MAX_VARYING_COMPONENTS.
> 
> Expand the BlitFramebuffer tests to cover these cases and start
> running them on the OpenGL backend.
> 
> BUG=angleproject:891
> 
> Change-Id: I4829585d2b6428ce0bc7509c4734d33709a0930b
> Reviewed-on: https://chromium-review.googlesource.com/582268
> Commit-Queue: Geoff Lang <geofflang@chromium.org>
> Reviewed-by: Kenneth Russell <kbr@chromium.org>
> Reviewed-by: Geoff Lang <geofflang@chromium.org>

TBR=geofflang@chromium.org,kbr@chromium.org

Change-Id: I220bc482194cf7fad5e7e732a6d043ce0d504d79
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: angleproject:891
Reviewed-on: https://chromium-review.googlesource.com/586428Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>