Add FlushForTesting to InterfacePtr and Binding.
Previously, when unit testing a class that is a client of a mojo
interface, there was no reliable way to detect that no message was sent.
This adds a FlushForTesting() method to mojo message pipe bindings,
which can be used to wait for a round trip, after which any messages
already sent will have been delivered; this can be used to test for the
absence of messages sent in response to some stimulus.
Review-Url: https://codereview.chromium.org/2280483002
Cr-Commit-Position: refs/heads/master@{#415920}
28 files changed
