Revise attribute binding interface

src/gpu/gl/GrGLProgram.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef GrGLProgram_DEFINED
 #define GrGLProgram_DEFINED
@@ skipping 42 matching lines @@
     void overrideBlend(GrBlendCoeff* srcCoeff, GrBlendCoeff* dstCoeff) const;
 
     const GrGLProgramDesc& getDesc() { return fDesc; }
 
     /**
      * Gets the GL program ID for this program.
      */
     GrGLuint programID() const { return fProgramID; }
 
     /**
-     * Some GL state that is relevant to programs is not stored per-program. In particular vertex
-     * attributes are global state. This struct is read and updated by GrGLProgram::setData to
-     * allow us to avoid setting this state redundantly.
+     * Some GL state that is relevant to programs is not stored per-program. In particular color
+     * and coverage attributes can be global state. This struct is read and updated by 
+     * GrGLProgram::setColor and GrGLProgram::setCoverage to allow us to avoid setting this state 
+     * redundantly.
      */
     struct SharedGLState {
         GrColor fConstAttribColor;
+        int     fConstAttribColorIndex;
         GrColor fConstAttribCoverage;
+        int     fConstAttribCoverageIndex;
 
         SharedGLState() { this->invalidate(); }
         void invalidate() {
             fConstAttribColor = GrColor_ILLEGAL;
+            fConstAttribColorIndex = -1;
             fConstAttribCoverage = GrColor_ILLEGAL;
+            fConstAttribCoverageIndex = -1;
         }
     };
 
     /**
      * The GrDrawState's view matrix along with the aspects of the render target determine the
      * matrix sent to GL. The size of the render target affects the GL matrix because we must
      * convert from Skia device coords to GL's normalized coords. Also the origin of the render
      * target may require us to perform a mirror-flip.
      */
     struct MatrixState {
@@ skipping 115 matching lines @@
     GrGLProgramDesc             fDesc;
     const GrGLContext&          fContext;
 
     GrGLUniformManager          fUniformManager;
     UniformHandles              fUniformHandles;
 
     typedef GrRefCnt INHERITED;
 };
 
 #endif