Use child processors to implement compose color filter.

src/gpu/GrProcOptInfo.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrProcOptInfo_DEFINED
 #define GrProcOptInfo_DEFINED
 
@@ skipping 32 matching lines @@
 
     // TODO: Once texture pixel configs quaries are updated, we no longer need this function.
     // For now this function will correctly tell us if we are using LCD text or not and should only
     // be called when looking at the coverage output.
     bool isFourChannelOutput() const { return !fInOut.isSingleComponent() &&
                                                fInOut.isLCDCoverage(); }
 
     GrColor color() const { return fInOut.color(); }
 
     GrColorComponentFlags validFlags() const {
-        return static_cast<GrColorComponentFlags>(fInOut.validFlags());
+        return fInOut.validFlags();
     }
 
     /**
      * Returns the index of the first effective color processor. If an intermediate processor
      * doesn't read its input or has a known output, then we can ignore all earlier processors
      * since they will not affect the final output. Thus the first effective processors index is
      * the index to the first processor that will have an effect on the final output.
      *
      * If processors before the firstEffectiveProcessorIndex() are removed, corresponding values
      * from inputColorIsUsed(), inputColorToEffectiveProcessor(), removeVertexAttribs(), and
@@ skipping 21 matching lines @@
     void internalCalc(const GrFragmentProcessor* const[], int cnt, bool initWillReadFragPosition);
 
     GrInvariantOutput fInOut;
     int fFirstEffectiveProcessorIndex;
     bool fInputColorIsUsed;
     GrColor fInputColor;
     bool fReadsFragPosition;
 };
 
 #endif