Delete all cached ephemeral apps at startup.

Delete all cached ephemeral apps at startup.

Ephemeral apps were cached when downloaded. The ephemeral app service
managed this cache, uninstalling old apps when the cache got full etc.
It also disabled ephemeral apps when they weren't running.

This change removes most of the ephemeral app service, and replaces it
with a simple implementation that deletes all cached apps at startup.
Some code to disable after they are stopped is left to keep the existing
tests passing.

Once the code to delete all cached ephemeral apps has been in stable
for a milestone, the remaining bits of the ephemeral app system will be
removed.

BUG=517735
Committed: https://crrev.com/59617d988124e582906ac72c2357738307f2e645
Cr-Commit-Position: refs/heads/master@{#357008}

[benwells, 2015-10-21 03:31:47]

benwells@chromium.org changed reviewers:
+ rdevlin.cronin@chromium.org

[Devlin, 2015-10-29 21:36:14]

Sorry for the delay; not sure how this one slipped through.

LGTM

[benwells, 2015-10-30 00:29:43]

On 2015/10/29 21:36:14, Devlin wrote:
> Sorry for the delay; not sure how this one slipped through.
> 
> LGTM

I forgot about it too :)

[benwells, 2015-10-30 00:29:49]

The CQ bit was checked by benwells@chromium.org

[commit-bot: I haz the power, 2015-10-30 00:30:35]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1415863002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1415863002/20001

[commit-bot: I haz the power, 2015-10-30 01:20:19]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-10-30 01:21:05]

Patchset 2 (id:??) landed as
https://crrev.com/59617d988124e582906ac72c2357738307f2e645
Cr-Commit-Position: refs/heads/master@{#357008}