Add "sample locations" feature to GrProcessor

include/gpu/GrProcessor.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrProcessor_DEFINED
 #define GrProcessor_DEFINED
 
@@ skipping 66 matching lines @@
     const GrTextureAccess& textureAccess(int index) const { return *fTextureAccesses[index]; }
 
     /** Shortcut for textureAccess(index).texture(); */
     GrTexture* texture(int index) const { return this->textureAccess(index).getTexture(); }
 
     /**
      * Platform specific built-in features that a processor can request for the fragment shader.
      */
     enum RequiredFeatures {
         kNone_RequiredFeatures             = 0,
-        kFragmentPosition_RequiredFeature  = 1
+        kFragmentPosition_RequiredFeature  = 1 << 0,
+        kSampleLocations_RequiredFeature   = 1 << 1
     };
 
     GR_DECL_BITFIELD_OPS_FRIENDS(RequiredFeatures);
 
     RequiredFeatures requiredFeatures() const { return fRequiredFeatures; }
 
     void* operator new(size_t size);
     void operator delete(void* target);
 
     void* operator new(size_t size, void* placement) {
@@ skipping 17 matching lines @@
      * Subclasses call this from their constructor to register GrTextureAccesses. The processor
      * subclass manages the lifetime of the accesses (this function only stores a pointer). The
      * GrTextureAccess is typically a member field of the GrProcessor subclass. This must only be
      * called from the constructor because GrProcessors are immutable.
      */
     virtual void addTextureAccess(const GrTextureAccess* textureAccess);
 
     bool hasSameTextureAccesses(const GrProcessor&) const;
 
     /**
-     * If the prcoessor will generate a backend-specific processor that will read the fragment
-     * position in the FS then it must call this method from its constructor. Otherwise, the
-     * request to access the fragment position will be denied.
+     * If the prcoessor will generate code that uses platform specific built-in features, then it
+     * must call these methods from its constructor. Otherwise, requests to use these features will
+     * be denied.
      */
     void setWillReadFragmentPosition() { fRequiredFeatures |= kFragmentPosition_RequiredFeature; }
+    void setWillUseSampleLocations() { fRequiredFeatures |= kSampleLocations_RequiredFeature; }
 
     void combineRequiredFeatures(const GrProcessor& other) {
         fRequiredFeatures |= other.fRequiredFeatures;
     }
 
     template <typename PROC_SUBCLASS> void initClassID() {
          static uint32_t kClassID = GenClassID();
          fClassID = kClassID;
     }
 
@@ skipping 19 matching lines @@
     static int32_t gCurrProcessorClassID;
 
     RequiredFeatures fRequiredFeatures;
 
     typedef GrProgramElement INHERITED;
 };
 
 GR_MAKE_BITFIELD_OPS(GrProcessor::RequiredFeatures);
 
 #endif