use SkBitmapProvider for shader-context

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 421 matching lines @@
         return false;
     }
 
 private:
     // This is essentially const, but not officially so it can be modified in
     // constructors.
     SkMatrix fLocalMatrix;
 
     // So the SkLocalMatrixShader can whack fLocalMatrix in its SkReadBuffer constructor.
     friend class SkLocalMatrixShader;
+    friend class SkBitmapProcShader;    // for computeTotalInverse()
 
     typedef SkFlattenable INHERITED;
 };
 
 #endif