Fixes for SkPictureShader.

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 331 matching lines @@
      *  @param tmx  The tiling mode to use when sampling the bitmap in the x-direction.
      *  @param tmy  The tiling mode to use when sampling the bitmap in the y-direction.
      *  @return     Returns a new shader object. Note: this function never returns null.
     */
     static SkShader* CreateBitmapShader(const SkBitmap& src,
                                         TileMode tmx, TileMode tmy);
 
     /** Call this to create a new shader that will draw with the specified picture.
      *
      *  @param src  The picture to use inside the shader (if not NULL, its ref count
-     *              is incremented).
+     *              is incremented). The SkPicture must not be changed after
+     *              successfully creating a picture shader.
+     *              FIXME: src cannot be const due to SkCanvas::drawPicture
      *  @param tmx  The tiling mode to use when sampling the bitmap in the x-direction.
      *  @param tmy  The tiling mode to use when sampling the bitmap in the y-direction.
      *  @return     Returns a new shader object. Note: this function never returns null.
     */
     static SkShader* CreatePictureShader(SkPicture* src, TileMode tmx, TileMode tmy);
 
     SK_TO_STRING_VIRT()
     SK_DEFINE_FLATTENABLE_TYPE(SkShader)
 
 protected:
@@ skipping 15 matching lines @@
     SkMatrix            fLocalMatrix;
     SkMatrix            fTotalInverse;
     uint8_t             fPaintAlpha;
     uint8_t             fTotalInverseClass;
     SkDEBUGCODE(SkBool8 fInSetContext;)
 
     typedef SkFlattenable INHERITED;
 };
 
 #endif