Add SkSourceGammaTreatment enum so we know how to create mips

src/effects/gradients/SkLinearGradient.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "Sk4fLinearGradient.h"
 #include "SkLinearGradient.h"
 
@@ skipping 400 matching lines @@
     SkPoint points[] = {{d->fRandom->nextUScalar1(), d->fRandom->nextUScalar1()},
                         {d->fRandom->nextUScalar1(), d->fRandom->nextUScalar1()}};
 
     SkColor colors[kMaxRandomGradientColors];
     SkScalar stopsArray[kMaxRandomGradientColors];
     SkScalar* stops = stopsArray;
     SkShader::TileMode tm;
     int colorCount = RandomGradientParams(d->fRandom, colors, &stops, &tm);
     auto shader = SkGradientShader::MakeLinear(points, colors, stops, colorCount, tm);
     const GrFragmentProcessor* fp = shader->asFragmentProcessor(d->fContext,
-        GrTest::TestMatrix(d->fRandom), NULL, kNone_SkFilterQuality);
+        GrTest::TestMatrix(d->fRandom), NULL, kNone_SkFilterQuality,
+        SkSourceGammaTreatment::kRespect);
     GrAlwaysAssert(fp);
     return fp;
 }
 
 /////////////////////////////////////////////////////////////////////
 
 void GrGLLinearGradient::emitCode(EmitArgs& args) {
     const GrLinearGradient& ge = args.fFp.cast<GrLinearGradient>();
     this->emitUniforms(args.fUniformHandler, ge);
     SkString t = args.fFragBuilder->ensureFSCoords2D(args.fCoords, 0);
     t.append(".x");
     this->emitColor(args.fFragBuilder,
                     args.fUniformHandler,
                     args.fGLSLCaps,
                     ge, t.c_str(),
                     args.fOutputColor,
                     args.fInputColor,
                     args.fTexSamplers);
 }
 
 /////////////////////////////////////////////////////////////////////
 
 const GrFragmentProcessor* SkLinearGradient::asFragmentProcessor(
                                                  GrContext* context,
                                                  const SkMatrix& viewm,
                                                  const SkMatrix* localMatrix,
-                                                 SkFilterQuality) const {
+                                                 SkFilterQuality,
+                                                 SkSourceGammaTreatment) const {
     SkASSERT(context);
 
     SkMatrix matrix;
     if (!this->getLocalMatrix().invert(&matrix)) {
         return nullptr;
     }
     if (localMatrix) {
         SkMatrix inv;
         if (!localMatrix->invert(&inv)) {
             return nullptr;
@@ skipping 295 matching lines @@
             this->shade4_dx_clamp<false, true>(dstC, count, fx, dx, invDx, dither);
         }
     } else {
         if (fApplyAlphaAfterInterp) {
             this->shade4_dx_clamp<true, false>(dstC, count, fx, dx, invDx, dither);
         } else {
             this->shade4_dx_clamp<false, false>(dstC, count, fx, dx, invDx, dither);
         }
     }
 }