Revert of Revert of Adding CopresenceState

Revert of Revert of Adding CopresenceState (patchset #1 id:1 of https://codereview.chromium.org/824593003/)

Reason for revert:
Reverting the revert as it causes compile failures. Will disable the test under valgrind instead.

Original issue's description:
> Revert of Adding CopresenceState (patchset #10 id:180001 of https://codereview.chromium.org/764673003/)
>
> Reason for revert:
> AudioDirectiveListTest.AddDirectiveMultiple started failing consistently on the linux valgrind memory fyi bot after this change.
>
> See http://build.chromium.org/p/chromium.memory.fyi/builders/Linux%20Tests%20%28valgrind%29%282%29/builds/41365 for details.
>
> I can't see any good reason why it would be failing in this way, on this bot, after this change, but I don't have time to investigate deeply.
>
> Original issue's description:
> > Adding CopresenceState, a central place to track the internal state of the copresence component. Classes can register to be notified of state changes (e.g. new directives or tokens). This provides the backend for the new debug UI.
> >
> > BUG=420889
> >
> > Committed: https://crrev.com/e8b0dbdbe00fd4cdfcc7db4fd4721ed74be4f928
> > Cr-Commit-Position: refs/heads/master@{#309315}
>
> TBR=rkc@chromium.org,xiyuan@chromium.org,ckehoe@chromium.org
> NOTREECHECKS=true
> NOTRY=true
> BUG=420889
>
> Committed: https://crrev.com/6b12c01b7bacec4b74594fb3437d3dbc01cc484c
> Cr-Commit-Position: refs/heads/master@{#309403}

TBR=rkc@chromium.org,xiyuan@chromium.org,ckehoe@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=420889
Committed: https://crrev.com/179f4a3a31fcb1cac02d93633ae37e41a7b394a4
Cr-Commit-Position: refs/heads/master@{#309405}

[benwells, 2014-12-22 07:31:06]

Created Revert of Revert of Adding CopresenceState

[commit-bot: I haz the power, 2014-12-22 07:31:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/806853003/1

[commit-bot: I haz the power, 2014-12-22 07:33:03]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-12-22 07:34:24]

Patchset 1 (id:??) landed as
https://crrev.com/179f4a3a31fcb1cac02d93633ae37e41a7b394a4
Cr-Commit-Position: refs/heads/master@{#309405}