Fix GPU blurring when using SkColorSpaceXformCanvas

Several GMs didn't draw at all (and asserted in debug builds). This fixes
all of that, so that the xform canvas (or even just pure-legaacy canvas)
doesn't accidentally blur in linear space by creating sRGB render target
contexts for sRGB-tagged inputs.

Bug: skia:
Change-Id: I37c567a1c5b0e004dc301e5c272c7b470ac5f4c8
Reviewed-on: https://skia-review.googlesource.com/66884
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
1 file changed