Make SkPictureShader and SkPictureImageFilter use const SkPictures

src/core/SkPictureShader.h

Index: src/core/SkPictureShader.h
diff --git a/src/core/SkPictureShader.h b/src/core/SkPictureShader.h
index 8df60306fddf4ccd8c9568180c490d7b944c533e..00aee9b0786630673572d6e97358f0ef2012a0c3 100644
--- a/src/core/SkPictureShader.h
+++ b/src/core/SkPictureShader.h
@@ -21,7 +21,7 @@ class SkPicture;
  */
 class SkPictureShader : public SkShader {
 public:
-    static SkPictureShader* Create(SkPicture*, TileMode, TileMode, const SkMatrix* = NULL);
+    static SkPictureShader* Create(const SkPicture*, TileMode, TileMode, const SkMatrix* = NULL);
     virtual ~SkPictureShader();
 
     virtual size_t contextSize() const SK_OVERRIDE;
@@ -38,12 +38,12 @@ protected:
     virtual Context* onCreateContext(const ContextRec&, void* storage) const SK_OVERRIDE;
 
 private:
-    SkPictureShader(SkPicture*, TileMode, TileMode, const SkMatrix* = NULL);
+    SkPictureShader(const SkPicture*, TileMode, TileMode, const SkMatrix* = NULL);
 
     SkShader* refBitmapShader(const SkMatrix&, const SkMatrix* localMatrix) const;
 
-    SkPicture*  fPicture;
-    TileMode    fTmx, fTmy;
+    const SkPicture*  fPicture;
+    TileMode          fTmx, fTmy;
 
     mutable SkMutex                 fCachedBitmapShaderMutex;
     mutable SkAutoTUnref<SkShader>  fCachedBitmapShader;