R1:3ab334af936d

Fix "reply" link in Differential

Summary:
Fixes the issue caused by rPa0af5b66437719dba6136579c051982ab275e6a0. Prior to
that patch, isCommentInNewFile() returned $comment->getIsNewFile(). While this
was often the wrong value, it came from the database and was the integer 1 if
true.

After the patch, the function returns 'true' as a boolean, which is passed to JS
and then back to PHP, interpreted as an integer, and evaluates to 0.

To avoid this issue in general, provide an isBool() method on…