Determine whether we can tweakAlphaForCoverage during Pipeline/XP creation.

include/gpu/GrInvariantOutput.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 GrInvariantOutput_DEFINED
 #define GrInvariantOutput_DEFINED
 
@@ skipping 192 matching lines @@
 
     bool isSolidWhite() const {
         return (fValidFlags == kRGBA_GrColorComponentFlags && 0xFFFFFFFF == fColor);
     }
 
     bool isSingleComponent() const { return fIsSingleComponent; }
 
     bool willUseInputColor() const { return fWillUseInputColor; }
     void resetWillUseInputColor() { fWillUseInputColor = true; }
 
+    bool allStagesMulInput() const { return !fNonMulStageFound; }
     void resetNonMulStageFound() { fNonMulStageFound = false; }
 
     bool isLCDCoverage() const { return fIsLCDCoverage; }
 
     SkDEBUGCODE(bool colorComponentsAllEqual() const;)
     /**
      * If alpha is valid, check that any valid R,G,B values are <= A
      */
     SkDEBUGCODE(bool validPreMulColor() const;)
 
     GrColor fColor;
     uint32_t fValidFlags;
     bool fIsSingleComponent;
     bool fNonMulStageFound;
     bool fWillUseInputColor;
     bool fIsLCDCoverage; // Temorary data member until texture pixel configs are updated
 
 };
 
 #endif