Cleanup some sRGB TODOs, mostly around setting GrPaint flags correctly

src/effects/SkXfermodeImageFilter.cpp

 /*
  * Copyright 2013 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkXfermodeImageFilter.h"
 
 #include "SkCanvas.h"
@@ skipping 161 matching lines @@
     
     if (background) {
         backgroundTex = background->asTextureRef(context);
     }
 
     if (foreground) {
         foregroundTex = foreground->asTextureRef(context);
     }
 
     GrPaint paint;
-    // SRGBTODO: AllowSRGBInputs?
     sk_sp<GrFragmentProcessor> bgFP;
 
     if (backgroundTex) {
         SkMatrix backgroundMatrix;
         backgroundMatrix.setIDiv(backgroundTex->width(), backgroundTex->height());
         backgroundMatrix.preTranslate(-SkIntToScalar(backgroundOffset.fX),
                                       -SkIntToScalar(backgroundOffset.fY));
         bgFP = GrTextureDomainEffect::Make(
                             backgroundTex.get(), nullptr, backgroundMatrix,
                             GrTextureDomain::MakeTexelDomain(backgroundTex.get(),
@@ skipping 48 matching lines @@
 
     paint.setPorterDuffXPFactory(SkXfermode::kSrc_Mode);
 
     sk_sp<GrDrawContext> drawContext(context->makeDrawContext(SkBackingFit::kApprox,
                                                               bounds.width(), bounds.height(),
                                                               kSkia8888_GrPixelConfig,
                                                               sk_ref_sp(source->getColorSpace())));
     if (!drawContext) {
         return nullptr;
     }
+    paint.setAllowSRGBInputs(drawContext->isGammaCorrect());
 
     SkMatrix matrix;
     matrix.setTranslate(SkIntToScalar(-bounds.left()), SkIntToScalar(-bounds.top()));
     drawContext->drawRect(GrNoClip(), paint, matrix, SkRect::Make(bounds));
 
     return SkSpecialImage::MakeFromGpu(SkIRect::MakeWH(bounds.width(), bounds.height()),
                                        kNeedNewImageUniqueID_SpecialImage,
                                        drawContext->asTexture(),
                                        sk_ref_sp(drawContext->getColorSpace()));
 }
 
 #endif