Make SkPictureShader and SkPictureImageFilter use const SkPictures

include/effects/SkPictureImageFilter.h

Index: include/effects/SkPictureImageFilter.h
diff --git a/include/effects/SkPictureImageFilter.h b/include/effects/SkPictureImageFilter.h
index fe07215c0b96525acd507c6cf54bc6130dae96f3..84d0c10016d027efb003ac31f8763c4a8ebb7566 100644
--- a/include/effects/SkPictureImageFilter.h
+++ b/include/effects/SkPictureImageFilter.h
@@ -16,7 +16,7 @@ public:
     /**
      *  Refs the passed-in picture.
      */
-    static SkPictureImageFilter* Create(SkPicture* picture) {
+    static SkPictureImageFilter* Create(const SkPicture* picture) {
         return SkNEW_ARGS(SkPictureImageFilter, (picture));
     }
 
@@ -24,15 +24,15 @@ public:
      *  Refs the passed-in picture. cropRect can be used to crop or expand the destination rect when
      *  the picture is drawn. (No scaling is implied by the dest rect; only the CTM is applied.)
      */
-    static SkPictureImageFilter* Create(SkPicture* picture, const SkRect& cropRect) {
+    static SkPictureImageFilter* Create(const SkPicture* picture, const SkRect& cropRect) {
         return SkNEW_ARGS(SkPictureImageFilter, (picture, cropRect));
     }
 
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkPictureImageFilter)
 
 protected:
-    explicit SkPictureImageFilter(SkPicture* picture);
-    SkPictureImageFilter(SkPicture* picture, const SkRect& cropRect);
+    explicit SkPictureImageFilter(const SkPicture* picture);
+    SkPictureImageFilter(const SkPicture* picture, const SkRect& cropRect);
     virtual ~SkPictureImageFilter();
     /*  Constructs an SkPictureImageFilter object from an SkReadBuffer.
      *  Note: If the SkPictureImageFilter object construction requires bitmap
@@ -48,8 +48,8 @@ protected:
                                 SkIRect* dst) const SK_OVERRIDE;
 
 private:
-    SkPicture* fPicture;
-    SkRect     fCropRect;
+    const SkPicture* fPicture;
+    SkRect           fCropRect;
     typedef SkImageFilter INHERITED;
 };