Introduce a //content/ API for dispatching notificationclick events.
This patch introduces a new public API to the content layer which should be
used for dispatching notificationclick events to a specific service worker.
The logic required for selecing the appropriate service worker is included
in the implementation of this class.
We're two CLs away from being able to test this stuff, which will be done
in the form of both layout tests and browser tests.
BUG=432527
Review URL: https://codereview.chromium.org/728763003
Cr-Commit-Position: refs/heads/master@{#307465}
12 files changed
