Rename MockMediaSource.Abort into Shutdown

Rename MockMediaSource.Abort into Shutdown

Also call ChunkDemuxer.Abort before shutting down the demuxer to test
that logic as well.

BUG=none

Committed: https://crrev.com/65465348ce9d806c00a2b6721aa8a3846d0382d8
Cr-Commit-Position: refs/heads/master@{#348287}

[servolk, 2015-09-10 00:50:24]

servolk@chromium.org changed reviewers:
+ wolenetz@chromium.org

[servolk, 2015-09-10 02:04:52]

servolk@chromium.org changed reviewers:
+ chcunningham@chromium.org

[servolk, 2015-09-10 22:33:00]

On 2015/09/10 02:04:56, servolk wrote:

ping

[wolenetz, 2015-09-10 23:35:40]

lgtm

[servolk, 2015-09-10 23:44:37]

The CQ bit was checked by servolk@chromium.org

[commit-bot: I haz the power, 2015-09-10 23:45:22]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1318643005/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1318643005/20001

[commit-bot: I haz the power, 2015-09-10 23:51:13]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-09-10 23:51:47]

Patchset 2 (id:??) landed as
https://crrev.com/65465348ce9d806c00a2b6721aa8a3846d0382d8
Cr-Commit-Position: refs/heads/master@{#348287}

[commit-bot: I haz the power, 2015-09-23 12:16:32]

Patchset 2 (id:??) landed as
https://crrev.com/65465348ce9d806c00a2b6721aa8a3846d0382d8
Cr-Commit-Position: refs/heads/master@{#348287}