Close all active PeerConnections upon OS suspend (relanding r290125 and r291213)

Close all active PeerConnections upon OS suspend (relanding r290125 and r291213)

Relanding these CLs, this time making sure to remove self from PowerMonitor's
observer list on the same thread as was added.

BUG=403618, 404767
Committed: https://crrev.com/eccaaa926e9448d1d6c5b62848954222ed3410af
Cr-Commit-Position: refs/heads/master@{#295297}

[vrk (LEFT CHROMIUM), 2014-09-15 21:43:43]

vrk@chromium.org changed reviewers:
+ jiayl@chromium.org, juberti@chromium.org, nasko@chromium.org

[vrk (LEFT CHROMIUM), 2014-09-15 21:43:44]

Trying to reland for the third time now.
Please take a look at the diff between patch 1 and 2.

nasko: peer_connection_tracker_messages.h OWNERS
jiayl/juberti: everything else

[jiayl, 2014-09-15 22:42:15]

lgtm

[dcheng, 2014-09-17 17:09:05]

dcheng@chromium.org changed reviewers:
+ dcheng@chromium.org

[dcheng, 2014-09-17 17:09:05]

IPC changes lgtm

[vrk (LEFT CHROMIUM), 2014-09-17 17:09:24]

The CQ bit was checked by vrk@chromium.org

[commit-bot: I haz the power, 2014-09-17 17:10:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/577483002/20001

[commit-bot: I haz the power, 2014-09-17 18:06:22]

Committed patchset #2 (id:20001) as 07488504ca5d15050afc26f6e60dfaf726cfd2fe

[commit-bot: I haz the power, 2014-09-17 18:07:11]

Patchset 2 (id:??) landed as
https://crrev.com/eccaaa926e9448d1d6c5b62848954222ed3410af
Cr-Commit-Position: refs/heads/master@{#295297}