Add an InvariantOutput for the XPF.

include/gpu/GrXferProcessor.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 GrXferProcessor_DEFINED
 #define GrXferProcessor_DEFINED
 
@@ skipping 162 matching lines @@
      * fractional pixel coverage generated by the fragment shader.
      *
      * This function considers the known color and coverage input into the xfer processor and
      * certain state information (colorWriteDisabled) to determine whether
      * coverage can be handled correctly.
      */
     // TODO: remove need for colorWriteDisabled once colorWriteDisabled is its own XP.
     virtual bool canApplyCoverage(const GrProcOptInfo& colorPOI, const GrProcOptInfo& coveragePOI,
                                   bool colorWriteDisabled) const = 0;
 
-    /**
-     * This function returns true if the destination pixel values will be read for blending during
-     * draw.
+
+    struct InvariantOutput {
+        bool        fWillBlendWithDst;
+        GrColor     fBlendedColor;
+        uint32_t    fBlendedColorFlags;
+    };
+
+    /** 
+     * This function returns known information about the output of the xfer processor produced by
+     * this xp factory. The invariant color information returned by this function refers to the
+     * final color produced after all blending.
      */
     // TODO: remove need for colorWriteDisabled once only XP can read dst.
-    virtual bool willBlendWithDst(const GrProcOptInfo& colorPOI, const GrProcOptInfo& coveragePOI,
-                                  bool colorWriteDisabled) const = 0;
+    virtual void getInvariantOutput(const GrProcOptInfo& colorPOI, const GrProcOptInfo& coveragePOI,
+                                    bool colorWriteDisabled, InvariantOutput*) const = 0;
 
     /**
      * Determines whether multiplying the computed per-pixel color by the pixel's fractional
      * coverage before the blend will give the correct final destination color. In general it
      * will not as coverage is applied after blending.
      */
     virtual bool canTweakAlphaForCoverage() const = 0;
 
-    virtual bool getOpaqueAndKnownColor(const GrProcOptInfo& colorPOI,
-                                        const GrProcOptInfo& coveragePOI, GrColor* solidColor,
-                                        uint32_t* solidColorKnownComponents) const = 0;
-
     bool isEqual(const GrXPFactory& that) const {
         if (this->classID() != that.classID()) {
             return false;
         }
         return this->onIsEqual(that);
     }
 
     /**
       * Helper for down-casting to a GrXPFactory subclass
       */
@@ skipping 29 matching lines @@
     enum {
         kIllegalXPFClassID = 0,
     };
     static int32_t gCurrXPFClassID;
 
     typedef GrProgramElement INHERITED;
 };
 
 #endif