Use same blob format for internal and external snapshots.

src/serialize.h

Index: src/serialize.h
diff --git a/src/serialize.h b/src/serialize.h
index 0c3465033388d00f84efe9b1022235751c4aaa0e..c524fcf5d03b18dc6ea47a036f88d92eda7ebdda 100644
--- a/src/serialize.h
+++ b/src/serialize.h
@@ -865,8 +865,8 @@ class SnapshotData : public SerializedData {
   SnapshotData(const SnapshotByteSink& sink, const Serializer& ser);
 
   // Used when consuming.
-  explicit SnapshotData(const byte* data, int size)
-      : SerializedData(const_cast<byte*>(data), size) {
+  explicit SnapshotData(const Vector<const byte> snapshot)
+      : SerializedData(const_cast<byte*>(snapshot.begin()), snapshot.length()) {
     CHECK(IsSane());
   }