Fix writePixels of sRGB data to legacy GPU surface

Adjusted unit test to verify this behavior.

Bug: skia:6547 chromium:713632 chromium:713702
Change-Id: I6240937b2faf6ccb6adfc9477dc85ae961cdbbb7
Reviewed-on: https://skia-review.googlesource.com/14279
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
diff --git a/src/gpu/GrContext.cpp b/src/gpu/GrContext.cpp
index 2a3852c..92be35c 100644
--- a/src/gpu/GrContext.cpp
+++ b/src/gpu/GrContext.cpp
@@ -400,7 +400,8 @@
         GrPaint paint;
         paint.addColorFragmentProcessor(std::move(fp));
         paint.setPorterDuffXPFactory(SkBlendMode::kSrc);
-        paint.setAllowSRGBInputs(true);
+        paint.setAllowSRGBInputs(SkToBool(dst->getColorSpace()) ||
+                                 GrPixelConfigIsSRGB(renderTargetContext->config()));
         SkRect rect = SkRect::MakeWH(SkIntToScalar(width), SkIntToScalar(height));
         renderTargetContext->drawRect(GrNoClip(), std::move(paint), GrAA::kNo, matrix, rect,
                                         nullptr);