Adds local coords to GrEffect system.

include/gpu/GrEffect.h

Index: include/gpu/GrEffect.h
===================================================================
--- include/gpu/GrEffect.h	(revision 8241)
+++ include/gpu/GrEffect.h	(working copy)
@@ -70,6 +70,20 @@
 public:
     SK_DECLARE_INST_COUNT(GrEffect)
 
+    /**
+     * The types of vertex coordinates available to an effect in the vertex shader. Effects can
+     * require their own vertex attribute but these coordinates are made available by the framework
+     * in all programs. kCustom_CoordsType is provided to signify that an alternative set of coords
+     * is used (usually an explicit vertex attribute) but its meaning is determined by the effect
+     * subclass.
+     */
+    enum CoordsType {
+        kLocal_CoordsType,
+        kPosition_CoordsType,
+
+        kCustom_CoordsType,
+    };
+
     virtual ~GrEffect();
 
     /**