Revert of Make LoadMonitoringExtensionHostQueue remove itself as an ExtensionHost observer at the...

Revert of Make LoadMonitoringExtensionHostQueue remove itself as an ExtensionHost observer at the correct tim… (patchset #4 id:160001 of https://codereview.chromium.org/995983002/)

Reason for revert:
Crashes (see crbug.com/467353).

Original issue's description:
> Make LoadMonitoringExtensionHostQueue remove itself as an ExtensionHost observer at the correct time.
> 
> "Extensions.ExtensionHostMonitoring.NumLoaded" UMA is now correctly recorded.
> I also cleaned up ExtensionHost a little to make it more obvious.
> 
> R=yoz@chromium.org
> TBR=sky@chromium.org
> 
> Committed: https://crrev.com/4eefc7b64335c6008a1e5218c230dadd733875a7
> Cr-Commit-Position: refs/heads/master@{#320536}

TBR=yoz@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

[not at google - send to devlin, 2015-03-16 17:06:30]

Created Revert of Make LoadMonitoringExtensionHostQueue remove itself as an
ExtensionHost observer at the correct tim…

[commit-bot: I haz the power, 2015-03-16 17:07:42]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-03-16 17:07:44]

The CQ bit was unchecked by commit-bot@chromium.org

[Yoyo Zhou, 2015-03-16 17:43:17]

LGTM

[not at google - send to devlin, 2015-03-16 17:43:43]

The CQ bit was checked by kalman@chromium.org

[commit-bot: I haz the power, 2015-03-16 17:43:50]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1012823002/1

[not at google - send to devlin, 2015-03-16 17:44:10]

You actually have to click [ ] to submit reverts. I didn't know that. Lucky you
lg'd that.

[commit-bot: I haz the power, 2015-03-16 17:44:37]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-03-16 17:44:39]

Failed to apply the patch.

[commit-bot: I haz the power, 2015-03-16 17:44:45]

The CQ bit was unchecked by commit-bot@chromium.org

[Yoyo Zhou, 2015-03-16 20:22:42]

crrev.com/320671 already reverts this, so I'm closing this one.