Create fragment processor for performing input color blend with child processor

include/effects/SkLumaColorFilter.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkLumaColorFilter_DEFINED
 #define SkLumaColorFilter_DEFINED
 
@@ skipping 11 matching lines @@
  *
  */
 class SK_API SkLumaColorFilter : public SkColorFilter {
 public:
     static SkColorFilter* Create();
 
     void filterSpan(const SkPMColor src[], int count, SkPMColor[]) const override;
 
 #if SK_SUPPORT_GPU
     bool asFragmentProcessors(GrContext*, GrProcessorDataManager*,
-                              SkTDArray<GrFragmentProcessor*>*) const override;
+                              SkTDArray<const GrFragmentProcessor*>*) const override;
 #endif
 
     SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkLumaColorFilter)
 
 protected:
     void flatten(SkWriteBuffer&) const override;
 
 private:
     SkLumaColorFilter();
 
     typedef SkColorFilter INHERITED;
 };
 
 #endif