Reland "Prefer the NV_framebuffer_blit extension over ANGLE"

This is a reland of 202ce887ec5d31c57716fd7798dcd640b2b2588b

Original change's description:
> Prefer the NV_framebuffer_blit extension over ANGLE
>
> The ANGLE/CHROMIUM glBlitFramebuffer requires full size blits, which
> is really bad for DMSAA. The NV extension does allow blits of
> sub-rectangles, so we prefer that one if it's available.
>
> Bug: skia:12176
> Bug: skia:12177
> Bug: skia:12234
> Bug: skia:12235
> Change-Id: I463ac631fff64ad564f294cf2f26be7410e8c356
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/430576
> Reviewed-by: Greg Daniel <egdaniel@google.com>
> Commit-Queue: Chris Dalton <csmartdalton@google.com>

Bug: skia:12176
Bug: skia:12177
Bug: skia:12234
Bug: skia:12235
Change-Id: I41d062f9894f5a81c78a37de27a288bc17812643
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/431817
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
4 files changed