When scrolling, _nextStepHandle is not being assigned to the async nextStep call.
This does not allow cancel() function to cancel the promise when changing files
resulting in incorrect text showing on the second file.
Bug: Issue 9409
Change-Id: I6969fdabf3c472b5a17d6901ceb2e0b19fa99921
(cherry picked from commit 8c090d3f23)