Implement color filter as GrGLEffect

include/gpu/GrEffect.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrEffect_DEFINED
 #define GrEffect_DEFINED
 
@@ skipping 77 matching lines @@
 
     /**
      * This function is used to perform optimizations. When called the color and validFlags params
      * indicate whether the input components to this effect in the FS will have known values.
      * validFlags is a bitfield of GrColorComponentFlags. The function updates both params to
      * indicate known values of its output. A component of the color param only has meaning if the
      * corresponding bit in validFlags is set.
      */
     virtual void getConstantColorComponents(GrColor* color, uint32_t* validFlags) const = 0;
 
+    /** Will this effect read the source color value? */
+    virtual bool willUseInputColor() const { return true; }
+
     /** This object, besides creating back-end-specific helper objects, is used for run-time-type-
         identification. The factory should be an instance of templated class,
         GrTBackendEffectFactory. It is templated on the subclass of GrEffect. The subclass must have
         a nested type (or typedef) named GLEffect which will be the subclass of GrGLEffect created
         by the factory.
 
         Example:
         class MyCustomEffect : public GrEffect {
         ...
             virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE {
@@ skipping 236 matching lines @@
 };                                                                                                \
 static SkAlignedSStorage<k_##NAME##_StorageSize> g_##NAME##_Storage;                              \
 static void* NAME##_RefLocation = (char*)g_##NAME##_Storage.get() + k_##NAME##_EffectRefOffset;   \
 static GrEffect* NAME##_Effect SkNEW_PLACEMENT_ARGS(g_##NAME##_Storage.get(), EFFECT_CLASS, ARGS);\
 static SkAutoTDestroy<GrEffect> NAME##_ad(NAME##_Effect);                                         \
 static GrEffectRef* NAME(GrEffect::CreateStaticEffectRef(NAME##_RefLocation, NAME##_Effect));     \
 static SkAutoTDestroy<GrEffectRef> NAME##_Ref_ad(NAME)
 
 
 #endif