make set3DMask virtual, so we can safely notify the shadercontext

src/core/SkFilterShader.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 SkFilterShader_DEFINED
 #define SkFilterShader_DEFINED
 
@@ skipping 12 matching lines @@
     public:
         // Takes ownership of shaderContext and calls its destructor.
         FilterShaderContext(const SkFilterShader&, SkShader::Context*, const ContextRec&);
         virtual ~FilterShaderContext();
 
         virtual uint32_t getFlags() const SK_OVERRIDE;
 
         virtual void shadeSpan(int x, int y, SkPMColor[], int count) SK_OVERRIDE;
         virtual void shadeSpan16(int x, int y, uint16_t[], int count) SK_OVERRIDE;
 
+        virtual void set3DMask(const SkMask* mask) SK_OVERRIDE {
+            // forward to our proxy
+            fShaderContext->set3DMask(mask);
+        }
+
     private:
         SkShader::Context* fShaderContext;
 
         typedef SkShader::Context INHERITED;
     };
 
     SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkFilterShader)
 
 protected:
 #ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
     SkFilterShader(SkReadBuffer&);
 #endif
     virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
     virtual Context* onCreateContext(const ContextRec&, void* storage) const SK_OVERRIDE;
 
 
 private:
     SkShader*       fShader;
     SkColorFilter*  fFilter;
 
     typedef SkShader INHERITED;
 };
 
 #endif