Potentially optimize some GrGLEffects for known input color values

src/effects/SkTableColorFilter.cpp

Index: src/effects/SkTableColorFilter.cpp
diff --git a/src/effects/SkTableColorFilter.cpp b/src/effects/SkTableColorFilter.cpp
index 083b54c4886691a9c3f7663e0e702533c2de1839..5bbe64f29f59e0578fbbbce7ecbe096acbb9214b 100644
--- a/src/effects/SkTableColorFilter.cpp
+++ b/src/effects/SkTableColorFilter.cpp
@@ -271,7 +271,7 @@ public:
                           const GrDrawEffect&,
                           EffectKey,
                           const char* outputColor,
-                          const char* inputColor,
+                          const GrGLSLExpr4& inputColor,
                           const TransformedCoordsArray&,
                           const TextureSamplerArray&) SK_OVERRIDE;
 
@@ -292,21 +292,21 @@ void GLColorTableEffect::emitCode(GrGLShaderBuilder* builder,
                                   const GrDrawEffect&,
                                   EffectKey,
                                   const char* outputColor,
-                                  const char* inputColor,
+                                  const GrGLSLExpr4& inputColor,
                                   const TransformedCoordsArray&,
                                   const TextureSamplerArray& samplers) {
 
     static const float kColorScaleFactor = 255.0f / 256.0f;
     static const float kColorOffsetFactor = 1.0f / 512.0f;
-    if (NULL == inputColor) {
+    if (inputColor.isOnes()) {
         // the input color is solid white (all ones).
         static const float kMaxValue = kColorScaleFactor + kColorOffsetFactor;
         builder->fsCodeAppendf("\t\tvec4 coord = vec4(%f, %f, %f, %f);\n",
                                kMaxValue, kMaxValue, kMaxValue, kMaxValue);
 
     } else {
-        builder->fsCodeAppendf("\t\tfloat nonZeroAlpha = max(%s.a, .0001);\n", inputColor);
-        builder->fsCodeAppendf("\t\tvec4 coord = vec4(%s.rgb / nonZeroAlpha, nonZeroAlpha);\n", inputColor);
+        builder->fsCodeAppendf("\t\tfloat nonZeroAlpha = %s;\n", GrGLSL::max(inputColor.a(), 0.0001f).c_str());
+        builder->fsCodeAppendf("\t\tvec4 coord = vec4(%s.rgb / nonZeroAlpha, nonZeroAlpha);\n", inputColor.c_str());
         builder->fsCodeAppendf("\t\tcoord = coord * %f + vec4(%f, %f, %f, %f);\n",
                               kColorScaleFactor,
                               kColorOffsetFactor, kColorOffsetFactor,