make set3DMask virtual, so we can safely notify the shadercontext

include/core/SkShader.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef SkShader_DEFINED
 #define SkShader_DEFINED
@@ skipping 167 matching lines @@
         virtual void shadeSpanAlpha(int x, int y, uint8_t alpha[], int count);
 
         /**
          *  Helper function that returns true if this shader's shadeSpan16() method
          *  can be called.
          */
         bool canCallShadeSpan16() {
             return SkShader::CanCallShadeSpan16(this->getFlags());
         }
 
+        // Notification from blitter::blitMask in case we need to see the non-alpha channels
+        virtual void set3DMask(const SkMask*) {}
+
     protected:
         // Reference to shader, so we don't have to dupe information.
         const SkShader& fShader;
 
         enum MatrixClass {
             kLinear_MatrixClass,            // no perspective
             kFixedStepInX_MatrixClass,      // fast perspective, need to call fixedStepInX() each
                                             // scanline
             kPerspective_MatrixClass        // slow perspective, need to mappoints each pixel
         };
@@ skipping 300 matching lines @@
     // constructors.
     SkMatrix fLocalMatrix;
 
     // So the SkLocalMatrixShader can whack fLocalMatrix in its SkReadBuffer constructor.
     friend class SkLocalMatrixShader;
 
     typedef SkFlattenable INHERITED;
 };
 
 #endif