change asABitmap to isABitmap on shader

src/effects/gradients/SkLinearGradient.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 SkLinearGradient_DEFINED
 #define SkLinearGradient_DEFINED
 
@@ skipping 10 matching lines @@
         LinearGradientContext(const SkLinearGradient&, const ContextRec&);
         ~LinearGradientContext() {}
 
         void shadeSpan(int x, int y, SkPMColor dstC[], int count) override;
         void shadeSpan16(int x, int y, uint16_t dstC[], int count) override;
 
     private:
         typedef SkGradientShaderBase::GradientShaderBaseContext INHERITED;
     };
 
-    BitmapType asABitmap(SkBitmap*, SkMatrix*, TileMode*) const override;
     GradientType asAGradient(GradientInfo* info) const override;
     bool asFragmentProcessor(GrContext*, const SkPaint&, const SkMatrix& viewM,
                              const SkMatrix*, GrColor*, GrProcessorDataManager*,
                              GrFragmentProcessor**) const override;
 
     SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkLinearGradient)
 
 protected:
     SkLinearGradient(SkReadBuffer& buffer);
     void flatten(SkWriteBuffer& buffer) const override;
     Context* onCreateContext(const ContextRec&, void* storage) const override;
 
 private:
     friend class SkGradientShader;
     typedef SkGradientShaderBase INHERITED;
     const SkPoint fStart;
     const SkPoint fEnd;
 };
 
 #endif