Consider 2,000 lines to be a large file for hints.

This is a fix for #4922... only part of Document.js was being processed
because it was considered a "large file" at 250 lines. 250 lines seems
a bit too conservative. We'll want to see if there are complaints about
memory usage and I think we'll also want to experiment a bit with how
we manage Tern.

But, it seems to me that a file the size of Document.js should not be
getting truncated hints.