Update invariant output computation for various texture effects.

src/gpu/effects/GrCustomCoordsTextureEffect.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrCustomCoordsTextureEffect.h"
 #include "GrInvariantOutput.h"
 #include "gl/builders/GrGLProgramBuilder.h"
@@ skipping 50 matching lines @@
                                                          kVec2f_GrSLType,
                                                          GrShaderVar::kAttribute_TypeModifier))) {
     this->addTextureAccess(&fTextureAccess);
 }
 
 bool GrCustomCoordsTextureEffect::onIsEqual(const GrGeometryProcessor& other) const {
     return true;
 }
 
 void GrCustomCoordsTextureEffect::onComputeInvariantOutput(GrInvariantOutput* inout) const {
-    if (GrPixelConfigIsOpaque(this->texture(0)->config())) {
+    if (GrPixelConfigIsAlphaOnly(this->texture(0)->config())) {
+        inout->mulByUnknownAlpha();
+    } else if (GrPixelConfigIsOpaque(this->texture(0)->config())) {
         inout->mulByUnknownOpaqueColor();
     } else {
         inout->mulByUnknownColor();
     }
 }
 
 const GrBackendGeometryProcessorFactory& GrCustomCoordsTextureEffect::getFactory() const {
     return GrTBackendGeometryProcessorFactory<GrCustomCoordsTextureEffect>::getInstance();
 }
 
@@ skipping 14 matching lines @@
     };
     SkShader::TileMode tileModes[] = {
         kTileModes[random->nextULessThan(SK_ARRAY_COUNT(kTileModes))],
         kTileModes[random->nextULessThan(SK_ARRAY_COUNT(kTileModes))],
     };
     GrTextureParams params(tileModes, random->nextBool() ? GrTextureParams::kBilerp_FilterMode :
                                                            GrTextureParams::kNone_FilterMode);
 
     return GrCustomCoordsTextureEffect::Create(textures[texIdx], params);
 }