Revise attribute binding interface

src/gpu/gl/GrGLProgram.h

Index: src/gpu/gl/GrGLProgram.h
===================================================================
--- src/gpu/gl/GrGLProgram.h	(revision 8462)
+++ src/gpu/gl/GrGLProgram.h	(working copy)
@@ -60,18 +60,23 @@
     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;
         }
     };