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

src/core/SkXfermode.cpp

Index: src/core/SkXfermode.cpp
diff --git a/src/core/SkXfermode.cpp b/src/core/SkXfermode.cpp
index 8c6eb2ca687f254c57f8ef6e19a8f72405f30c9e..2d6fab732dc01c1cfb2c7aa0c3a93f57cc19c7b8 100644
--- a/src/core/SkXfermode.cpp
+++ b/src/core/SkXfermode.cpp
@@ -952,7 +952,7 @@ public:
 
             // We don't try to optimize for this case at all
             if (NULL == inputColor) {
-                builder->fsCodeAppendf("\t\tconst vec4 ones = %s;\n", GrGLSLOnesVecf(4));
+                builder->fsCodeAppendf("\t\tconst vec4 ones = vec4(1);\n");
                 inputColor = "ones";
             }
             builder->fsCodeAppendf("\t\t// SkXfermode::Mode: %s\n", SkXfermode::ModeName(mode));