[Media Router] Simplify unit tests

This patch removes various 'trampoline' methods used to handle move-only
parameters or set expectations on callback parameters.  In most cases these
can be replaced by standard GMock idioms.

This patch does keep RouteResponseCallbackHandler, which is used to unpack and
set expectations on parts of RouteRequestResult.  A duplicate copy is removed in
this patch.

Bug: 851567
Change-Id: I4309327df4a437b4aa565837c4f7b0861dd3f208
Reviewed-on: https://chromium-review.googlesource.com/c/1459327
Commit-Queue: mark a. foltz <mfoltz@chromium.org>
Reviewed-by: Takumi Fujimoto <takumif@chromium.org>
Cr-Commit-Position: refs/heads/master@{#630194}
9 files changed