Add Mojo interfaces for out-of-process proxy resolver.

See:
https://docs.google.com/a/chromium.org/document/d/1n5hr4KJhZl2A4MicTfmyiHPdiKp7kmUoWXnRBN8SrZE/edit#

BUG=11746

Review URL: https://codereview.chromium.org/900433003

Cr-Commit-Position: refs/heads/master@{#314509}
4 files changed