Revert of Move DstCopy on gpu into the GrXferProcessor.

src/gpu/GrProgramDesc.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 GrProgramDesc_DEFINED
 #define GrProgramDesc_DEFINED
 
@@ skipping 37 matching lines @@
 
     bool operator!= (const GrProgramDesc& other) const {
         return !(*this == other);
     }
 
     static bool Less(const GrProgramDesc& a, const GrProgramDesc& b) {
         return memcmp(a.asKey(), b.asKey(), a.keyLength() & ~0x3) < 0;
     }
 
     struct KeyHeader {
+        uint8_t                     fDstReadKey;   // set by GrGLShaderBuilder if there
+                                                   // are effects that must read the dst.
+                                                   // Otherwise, 0.
         uint8_t                     fFragPosKey;   // set by GrGLShaderBuilder if there are
                                                    // effects that read the fragment position.
                                                    // Otherwise, 0.
 
         int8_t                      fColorEffectCnt;
         int8_t                      fCoverageEffectCnt;
     };
 
     int numColorEffects() const {
         return this->header().fColorEffectCnt;
     }
 
     int numCoverageEffects() const {
         return this->header().fCoverageEffectCnt;
     }
 
     int numTotalEffects() const { return this->numColorEffects() + this->numCoverageEffects(); }
 
     // This should really only be used internally, base classes should return their own headers
     const KeyHeader& header() const { return *this->atOffset<KeyHeader, kHeaderOffset>(); }
 
+    // A struct to communicate descriptor information to the program descriptor builder
+    struct DescInfo {
+        bool operator==(const DescInfo& that) const {
+            return fReadsDst == that.fReadsDst &&
+                   fReadsFragPosition == that.fReadsFragPosition;
+        }
+        bool operator!=(const DescInfo& that) const { return !(*this == that); };
+
+        // These flags give aggregated info on the processor stages that are used when building
+        // programs.
+        bool            fReadsDst;
+        bool            fReadsFragPosition;
+    };
+
 private:
     template<typename T, size_t OFFSET> T* atOffset() {
         return reinterpret_cast<T*>(reinterpret_cast<intptr_t>(fKey.begin()) + OFFSET);
     }
 
     template<typename T, size_t OFFSET> const T* atOffset() const {
         return reinterpret_cast<const T*>(reinterpret_cast<intptr_t>(fKey.begin()) + OFFSET);
     }
 
     void finalize() {
@@ skipping 27 matching lines @@
         kPreAllocSize = kHeaderOffset + kHeaderSize +
                         kMaxPreallocProcessors * sizeof(uint32_t) * kIntsPerProcessor,
     };
 
     SkSTArray<kPreAllocSize, uint8_t, true> fKey;
 
     friend class GrGLProgramDescBuilder;
 };
 
 #endif