Add TODO to implement 'bookmarking' for the streaming stream.

src/scanner-character-streams.h

Index: src/scanner-character-streams.h
diff --git a/src/scanner-character-streams.h b/src/scanner-character-streams.h
index 36d84bc0f6b5d82a16b005bef0ea737138642a1f..369cb28e7ba9b7ab29558e77195622a248da8abe 100644
--- a/src/scanner-character-streams.h
+++ b/src/scanner-character-streams.h
@@ -83,6 +83,8 @@ class Utf8ToUtf16CharacterStream: public BufferedUtf16CharacterStream {
 
 // ExternalStreamingStream is a wrapper around an ExternalSourceStream (see
 // include/v8.h) subclass implemented by the embedder.
+//
+// TODO(vogelheim): Implement (Set|ResetTo)Bookmark methods for this stream.
 class ExternalStreamingStream : public BufferedUtf16CharacterStream {
  public:
   ExternalStreamingStream(ScriptCompiler::ExternalSourceStream* source_stream,