Express (GLSL expression, possibly known value) pairs as a class

src/effects/SkColorMatrixFilter.cpp

Index: src/effects/SkColorMatrixFilter.cpp
diff --git a/src/effects/SkColorMatrixFilter.cpp b/src/effects/SkColorMatrixFilter.cpp
index 484836a5b30c994875bbfae27dfd9872f7d2824e..1e3c779ec661d36e1e8e4aca12acdc769b9555b7 100644
--- a/src/effects/SkColorMatrixFilter.cpp
+++ b/src/effects/SkColorMatrixFilter.cpp
@@ -410,7 +410,7 @@ public:
 
             if (NULL == inputColor) {
                 // could optimize this case, but we aren't for now.
-                inputColor = GrGLSLOnesVecf(4);
+                inputColor = "vec4(1)";
             }
             // The max() is to guard against 0 / 0 during unpremul when the incoming color is
             // transparent black.