Update invariant output computation for various texture effects.

src/gpu/effects/GrTextureDomain.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 "gl/builders/GrGLProgramBuilder.h"
 #include "GrTextureDomain.h"
 #include "GrInvariantOutput.h"
@@ skipping 253 matching lines @@
     return GrTBackendFragmentProcessorFactory<GrTextureDomainEffect>::getInstance();
 }
 
 bool GrTextureDomainEffect::onIsEqual(const GrFragmentProcessor& sBase) const {
     const GrTextureDomainEffect& s = sBase.cast<GrTextureDomainEffect>();
     return this->fTextureDomain == s.fTextureDomain;
 }
 
 void GrTextureDomainEffect::onComputeInvariantOutput(GrInvariantOutput* inout) const {
     if (GrTextureDomain::kDecal_Mode == fTextureDomain.mode()) { // TODO: helper
-        inout->mulByUnknownColor();
+        if (GrPixelConfigIsAlphaOnly(this->texture(0)->config())) {
+            inout->mulByUnknownAlpha();
+        } else {
+            inout->mulByUnknownColor();
+        }
     } else {
         this->updateInvariantOutputForModulation(inout);
     }
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 GR_DEFINE_FRAGMENT_PROCESSOR_TEST(GrTextureDomainEffect);
 
 GrFragmentProcessor* GrTextureDomainEffect::TestCreate(SkRandom* random,
@@ skipping 12 matching lines @@
     const SkMatrix& matrix = GrProcessorUnitTest::TestMatrix(random);
     bool bilerp = mode != GrTextureDomain::kRepeat_Mode ? random->nextBool() : false;
     GrCoordSet coords = random->nextBool() ? kLocal_GrCoordSet : kPosition_GrCoordSet;
     return GrTextureDomainEffect::Create(textures[texIdx],
                                          matrix,
                                          domain,
                                          mode,
                                          bilerp ? GrTextureParams::kBilerp_FilterMode : GrTextureParams::kNone_FilterMode,
                                          coords);
 }