Add a full end-to-end test for Background Fetch

Add a full end-to-end test for Background Fetch

This adds a full end-to-end test for Background Fetch that starts a
Fetch at the Mojo service implementation, provides fake responses
through the download system and invokes the Service Worker event.

There's a ton of TODOs for change-detector tests as we continue to build
up the rest of the API's functionality.

BUG=692579
Review-Url: https://codereview.chromium.org/2786973002
Cr-Commit-Position: refs/heads/master@{#461418}
Committed: https://chromium.googlesource.com/chromium/src/+/c8d12aafd304aa6a16e73c4bc37ebf270bdee9df

[Peter Beverloo, 2017-03-30 14:48:09]

peter@chromium.org changed reviewers:
+ harkness@chromium.org

[Peter Beverloo, 2017-03-30 14:48:10]

+harkness, PTAL

[harkness, 2017-04-03 08:17:10]

lgtm

[Peter Beverloo, 2017-04-03 12:27:46]

The CQ bit was checked by peter@chromium.org

[commit-bot: I haz the power, 2017-04-03 12:27:53]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-04-03 13:31:39]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1491222466689210, "parent_rev":
"3f2db89d6d660abe00760144e734ccb9963cce2a", "commit_rev":
"c8d12aafd304aa6a16e73c4bc37ebf270bdee9df"}

[commit-bot: I haz the power, 2017-04-03 13:32:41]

Description was changed from

==========
Add a full end-to-end test for Background Fetch

This adds a full end-to-end test for Background Fetch that starts a
Fetch at the Mojo service implementation, provides fake responses
through the download system and invokes the Service Worker event.

There's a ton of TODOs for change-detector tests as we continue to build
up the rest of the API's functionality.

BUG=692579
==========

to

==========
Add a full end-to-end test for Background Fetch

This adds a full end-to-end test for Background Fetch that starts a
Fetch at the Mojo service implementation, provides fake responses
through the download system and invokes the Service Worker event.

There's a ton of TODOs for change-detector tests as we continue to build
up the rest of the API's functionality.

BUG=692579

Review-Url: https://codereview.chromium.org/2786973002
Cr-Commit-Position: refs/heads/master@{#461418}
Committed:
https://chromium.googlesource.com/chromium/src/+/c8d12aafd304aa6a16e73c4bc37e...
==========

[commit-bot: I haz the power, 2017-04-03 13:32:41]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/c8d12aafd304aa6a16e73c4bc37e...