Two (related) changes here:

Two (related) changes here:

1) Our older iOS devices failed our sRGB tests, due to precision issues
with alpha. At this point, we only test on iPadMini 4, and that appears
not to have any problems.

2) iOS devices still don't have the sRGB texture decode extension. But,
some clients have no interest in mixing legacy/color-correct rendering,
and would like to use sRGB on these devices. This GrContextOptions flag
enables sRGB support in those cases.

Adjust the test code to produce sRGB capable contexts on these devices,
but only for configs that have a color space. (See comment).

BUG=skia:4148

Committed: https://skia.googlesource.com/skia/+/9db12d2341f3f8722c8b90b11dd4cce138a8a64e
Review-Url: https://codereview.chromium.org/2539993002