Allow GrGLEffects to produce variable length keys.

src/effects/SkColorMatrixFilter.cpp

Index: src/effects/SkColorMatrixFilter.cpp
diff --git a/src/effects/SkColorMatrixFilter.cpp b/src/effects/SkColorMatrixFilter.cpp
index c24a2b773ad74678a8d0c7e244d9646a72ad9005..31a76ab9cdfecb7d8271d7143a14bf8a399cb609 100644
--- a/src/effects/SkColorMatrixFilter.cpp
+++ b/src/effects/SkColorMatrixFilter.cpp
@@ -391,7 +391,7 @@ public:
     class GLEffect : public GrGLEffect {
     public:
         // this class always generates the same code.
-        static EffectKey GenKey(const GrDrawEffect&, const GrGLCaps&) { return 0; }
+        static void GenKey(const GrDrawEffect&, const GrGLCaps&, GrEffectKeyBuilder* b) {}
 
         GLEffect(const GrBackendEffectFactory& factory,
                  const GrDrawEffect&)
@@ -400,7 +400,7 @@ public:
 
         virtual void emitCode(GrGLShaderBuilder* builder,
                               const GrDrawEffect&,
-                              EffectKey,
+                              const GrEffectKey&,
                               const char* outputColor,
                               const char* inputColor,
                               const TransformedCoordsArray&,