Create helper functions to use in computeInvariantOutput calls

src/gpu/effects/GrBicubicEffect.cpp

 /*
  * Copyright 2014 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 "GrBicubicEffect.h"
 
@@ skipping 153 matching lines @@
 
 bool GrBicubicEffect::onIsEqual(const GrProcessor& sBase) const {
     const GrBicubicEffect& s = sBase.cast<GrBicubicEffect>();
     return this->textureAccess(0) == s.textureAccess(0) &&
            !memcmp(fCoefficients, s.coefficients(), 16) &&
            fDomain == s.fDomain;
 }
 
 void GrBicubicEffect::onComputeInvariantOutput(InvariantOutput* inout) const {
     // FIXME: Perhaps we can do better.
-    inout->fValidFlags = 0;
-    inout->fIsSingleComponent = false;
-    return;
+    inout->mulByUnknownAlpha();
 }
 
 GR_DEFINE_FRAGMENT_PROCESSOR_TEST(GrBicubicEffect);
 
 GrFragmentProcessor* GrBicubicEffect::TestCreate(SkRandom* random,
                                                  GrContext* context,
                                                  const GrDrawTargetCaps&,
                                                  GrTexture* textures[]) {
     int texIdx = random->nextBool() ? GrProcessorUnitTest::kSkiaPMTextureIdx :
                                       GrProcessorUnitTest::kAlphaTextureIdx;
@@ skipping 29 matching lines @@
             // Use bilerp to handle rotation or fractional translation.
             *filterMode = GrTextureParams::kBilerp_FilterMode;
         }
         return false;
     }
     // When we use the bicubic filtering effect each sample is read from the texture using
     // nearest neighbor sampling.
     *filterMode = GrTextureParams::kNone_FilterMode;
     return true;
 }