Deduplicate typefaces across sub-pictures

include/core/SkPicture.h

Index: include/core/SkPicture.h
diff --git a/include/core/SkPicture.h b/include/core/SkPicture.h
index baef45ded0263e59516ca959b609b989ce9873c7..774b5424428d2684cbfaa7359090148e4fa09b46 100644
--- a/include/core/SkPicture.h
+++ b/include/core/SkPicture.h
@@ -18,7 +18,9 @@ class SkBitmap;
 class SkCanvas;
 class SkPictureData;
 class SkPixelSerializer;
+class SkRefCntSet;
 class SkStream;
+class SkTypefacePlayback;
 class SkWStream;
 struct SkPictInfo;
 
@@ -163,6 +165,12 @@ private:
     friend class SkEmptyPicture;
     template <typename> friend class SkMiniPicture;
 
+    void serialize(SkWStream*, SkPixelSerializer*, SkRefCntSet* typefaces) const;
+    static SkPicture* CreateFromStream(SkStream*,
+                                       InstallPixelRefProc proc,
+                                       SkTypefacePlayback*);
+    friend class SkPictureData;
+
     virtual int numSlowPaths() const = 0;
     friend struct SkPathCounter;