Bug 846933 - Comment class TokenStream.  r=nnethercote.

--HG--
extra : rebase_source : ab0549c7e56e85fa43a3d714f68050ffb7a65e83
Bug 854137 - Don't hold pointers to yield nodes in the parse tree.  r=jorendorff.

--HG--
extra : rebase_source : 43261a7168c47f4bdaadcb2747017fec63b8937d