Revert of Reset accessibility if it gets out of sync.

Revert of Reset accessibility if it gets out of sync. (patchset #10 id:180001 of https://codereview.chromium.org/625443002/)

Reason for revert:
Suspecting this for failing test:

https://build.chromium.org/p/chromium.mac/builders/Mac%2010.6%20Tests%20%28dbg%29%281%29/builds/53374/steps/content_browsertests/logs/ResetBrowserAccessibilityManager

Original issue's description:
> Reset accessibility if it gets out of sync.
>
> Previously if the browser got an accessibility IPC it was unable to
> interpret, it killed the renderer. This change makes it reset the
> accessibility state instead so we're tolerant of corner cases that
> are very difficult to completely eliminate in practice.
>
> The accessibility reset is designed to be safe, it throws away all
> accessibility state on the browser side and waits for an IPC from
> the renderer acknowledging the renderer reset as well.
>
> BUG=372478
>
> Committed: https://crrev.com/0c5e8d16661df7e08c708997f24c0a3070e58080
> Cr-Commit-Position: refs/heads/master@{#298297}

TBR=nasko@chromium.org,tsepez@chromium.org,mkwst@chromium.org,dmazzoni@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=372478
Committed: https://crrev.com/883b07f3e5555a5efad7771e968e950725e3d748
Cr-Commit-Position: refs/heads/master@{#298315}

[jackhou1, 2014-10-07 00:23:48]

Created Revert of Reset accessibility if it gets out of sync.

[commit-bot: I haz the power, 2014-10-07 00:27:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/629413002/1

[commit-bot: I haz the power, 2014-10-07 00:33:05]

Committed patchset #1 (id:1) as cf2aba9397a2cfbf2dd1651b2ccb60fd1b3de65c

[commit-bot: I haz the power, 2014-10-07 00:33:47]

Patchset 1 (id:??) landed as
https://crrev.com/883b07f3e5555a5efad7771e968e950725e3d748
Cr-Commit-Position: refs/heads/master@{#298315}