GitLab

Some functions ended up having more overloaded versions than
is reasonable; templates to the rescue.

1. Move MaybeReply from .h to .cc, made it into a template, and
   used it in a few additional cases.
2. Made MaybeReply take a base::Location&, rather than hard-code
   the location of the helper function itself.
3. Created a template for Reply and ReplyClosure in the unit test
   suite.

Bug: 775415
Change-Id: Ie2c9e31defd045535845d198c658f0859ef99228
Reviewed-on: https://chromium-review.googlesource.com/1114615
Commit-Queue: Elad Alon <eladalon@chromium.org>
Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#571101}