This is implementing one side of the mojo Permission service: requesting
a permission. This is being used by the Geolocation code in the renderer
process.
This CL is creating all the required hooks for the permission service
and can be used as a base to increment on top of.
BUG=430238, 420497
Review URL: https://codereview.chromium.org/722153003
Cr-Commit-Position: refs/heads/master@{#304227}