Revert of remvoe duplicate impl for SkImageInfo flattening

include/core/SkPicture.h

Index: include/core/SkPicture.h
diff --git a/include/core/SkPicture.h b/include/core/SkPicture.h
index cd6b3bcbb1515ffadc62aa5dbf199d8b9cb5b6ee..bce343ec040d28bdaef60f4c8cd1b8d9e0ce8d7b 100644
--- a/include/core/SkPicture.h
+++ b/include/core/SkPicture.h
@@ -220,11 +220,10 @@
     // V14: Add flags word to PathRef serialization
     // V15: Remove A1 bitmpa config (and renumber remaining configs)
     // V16: Move SkPath's isOval flag to SkPathRef
-    // V17: Changes to PixelRef to store SkImageInfo
 #ifndef DELETE_THIS_CODE_WHEN_SKPS_ARE_REBUILT_AT_V16_AND_ALL_OTHER_INSTANCES_TOO
     static const uint32_t PRIOR_PICTURE_VERSION = 15;  // TODO: remove when .skps regenerated
 #endif
-    static const uint32_t PICTURE_VERSION = 17;
+    static const uint32_t PICTURE_VERSION = 16;
 
     // fPlayback, fRecord, fWidth & fHeight are protected to allow derived classes to
     // install their own SkPicturePlayback-derived players,SkPictureRecord-derived