Revert of Reimplement automation API on top of C++-backed AXTree.

Revert of Reimplement automation API on top of C++-backed AXTree. (patchset #15 id:280001 of https://codereview.chromium.org/1155183006/)

Reason for revert:
Reverting as likely cause of bug 502311

Original issue's description:
> Reimplement automation API on top of C++-backed AXTree.
>
> Design doc: https://docs.google.com/a/google.com/document/d/1nKMfTbS5W6uGlqRHf0XRZLVzAcKD_vqu8lw7l9zHoBw/edit?usp=sharing
>
> BUG=495323
>
> Committed: https://crrev.com/0e90449a7c9bd8f051fce4988a8cccd6c1c64661
> Cr-Commit-Position: refs/heads/master@{#335183}

TBR=dcheng@chromium.org,aboxhall@chromium.org,dtseng@chromium.org,kalman@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=495323
Committed: https://crrev.com/2e4a6c574402c5c9c4f6f7f6690dafef6b70898b
Cr-Commit-Position: refs/heads/master@{#335343}

[dmazzoni, 2015-06-19 20:59:25]

Created Revert of Reimplement automation API on top of C++-backed AXTree.

[commit-bot: I haz the power, 2015-06-19 21:00:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1198613002/1

[commit-bot: I haz the power, 2015-06-19 21:02:13]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-19 21:03:17]

Patchset 1 (id:??) landed as
https://crrev.com/2e4a6c574402c5c9c4f6f7f6690dafef6b70898b
Cr-Commit-Position: refs/heads/master@{#335343}