Add capture snapshot as data to SkWriter32, use it to optimise record->playback.

src/core/SkPicturePlayback.cpp

Index: src/core/SkPicturePlayback.cpp
diff --git a/src/core/SkPicturePlayback.cpp b/src/core/SkPicturePlayback.cpp
index 8b8c6b0862dad7bb6d0bc643de3b09b0abca4fd7..01dd8598ec797ad0910414d61817bd53fd15504e 100644
--- a/src/core/SkPicturePlayback.cpp
+++ b/src/core/SkPicturePlayback.cpp
@@ -84,13 +84,8 @@ SkPicturePlayback::SkPicturePlayback(const SkPictureRecord& record, bool deepCop
         fBoundingHierarchy->flushDeferredInserts();
     }
 
-    {
-        size_t size = writer.bytesWritten();
-        void* buffer = sk_malloc_throw(size);
-        writer.flatten(buffer);
-        SkASSERT(!fOpData);
-        fOpData = SkData::NewFromMalloc(buffer, size);
-    }
+    SkASSERT(!fOpData);
+    fOpData = writer.snapshotAsData();
 
     // copy over the refcnt dictionary to our reader
     record.fFlattenableHeap.setupPlaybacks();