Allow multiple Mojo handlers on a single WebUI.

This CL changes MojoWebUIController to use a templated
AddHandlerToRegistry function which allows subclasses to add multiple
interfaces to the binder registry.

TBR=khorimoto@chromium.org

Change-Id: I943e3d583c9a3c8bb08873001cc533c2d23a0bcf
Reviewed-on: https://chromium-review.googlesource.com/991497
Commit-Queue: calamity <calamity@chromium.org>
Reviewed-by: calamity <calamity@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Ken Rockot <rockot@chromium.org>
Reviewed-by: Sam McNally <sammc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551256}
20 files changed