Mojo Example that demos the difference between providing and requesting an interface.

BUG=
R=viettrungluu@chromium.org, yzshen@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/405bc1690e199f5d4bf5d75b998c595c87f914f8

Review URL: https://codereview.chromium.org/733563002