added support for PLS path rendering

src/gpu/GrPrimitiveProcessor.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrPrimitiveProcessor_DEFINED
 #define GrPrimitiveProcessor_DEFINED
 
@@ skipping 29 matching lines @@
  * can be updated alongside the GrBatchTracker struct itself, ultimately allowing the
  * GrPrimitiveProcessor complete control of how it gets data into the fragment shader as long as
  * it emits the appropriate color, or none at all, as directed.
  */
 
 class GrGLSLCaps;
 class GrGLSLPrimitiveProcessor;
 
 struct GrInitInvariantOutput;
 
+// Describes the state of pixel local storage with respect to the current draw. 
+enum GrPixelLocalStorageState {
+    // The draw is actively updating PLS.
+    kDraw_State,

[bsalomon, 2016/01/13 19:15:34]

The style is that tag after the "_" is the name of the enum type, e.g.
kDraw_GrPixelLocalStorageState.

+    // The draw is a "finish" operation which is reading from PLS and writing color.
+    kFinish_State,
+    // The draw does not use PLS.
+    kDisabled_State
+};
+
 /*
  * This class allows the GrPipeline to communicate information about the pipeline to a
  * GrBatch which should be forwarded to the GrPrimitiveProcessor(s) created by the batch.
  * These are not properly part of the pipeline because they assume the specific inputs
  * that the batch provided when it created the pipeline. Identical pipelines may be
  * created by different batches with different input assumptions and therefore different
  * computed optimizations. It is the batch-specific optimizations that allow the pipelines
  * to be equal.
  */
 class GrXPOverridesForBatch {
@@ skipping 132 matching lines @@
      */
     virtual void getGLSLProcessorKey(const GrGLSLCaps& caps,
                                      GrProcessorKeyBuilder* b) const = 0;
 
 
     /** Returns a new instance of the appropriate *GL* implementation class
         for the given GrProcessor; caller is responsible for deleting
         the object. */
     virtual GrGLSLPrimitiveProcessor* createGLSLInstance(const GrGLSLCaps& caps) const = 0;
 
-    bool isPathRendering() const { return fIsPathRendering; }
+    virtual bool isPathRendering() const { return false; }
 
     /**
      * No Local Coord Transformation is needed in the shader, instead transformed local coords will
      * be provided via vertex attribute.
      */
     virtual bool hasTransformedLocalCoords() const = 0;
 
+    virtual GrPixelLocalStorageState getPixelLocalStorageState() const { return kDisabled_State; }
+
+    /**
+     * If non-null, overrides the dest color returned by GrGLSLFragmentShaderBuilder::dstColor().
+     */
+    virtual const char* getDestColorOverride() const { return nullptr; }
+    
 protected:
-    GrPrimitiveProcessor(bool isPathRendering)
+    GrPrimitiveProcessor()
         : fNumAttribs(0)
-        , fVertexStride(0)
-        , fIsPathRendering(isPathRendering) {}
+        , fVertexStride(0) {}
 
     Attribute fAttribs[kMaxVertexAttribs];
     int fNumAttribs;
     size_t fVertexStride;
 
 private:
     void notifyRefCntIsZero() const final {};
     virtual bool hasExplicitLocalCoords() const = 0;
 
-    bool fIsPathRendering;
-
     typedef GrProcessor INHERITED;
 };
 
 #endif