Remove unused ui::AXPlatformNode pointer from BrowserAccessibility.

Remove unused ui::AXPlatformNode pointer from BrowserAccessibility.

A while ago, we thought we would keep the the platform node as a seperate
object.  Most of this was removed in
https://codereview.chromium.org/2886353003 but we missed this.

BUG=703369
Review-Url: https://codereview.chromium.org/2930413004
Cr-Commit-Position: refs/heads/master@{#479644}
Committed: https://chromium.googlesource.com/chromium/src/+/4d2a90d730038e5608c9b89256746636b64b292f

[dougt, 2017-06-13 20:42:42]

The CQ bit was checked by dougt@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-06-13 20:43:11]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-06-13 22:00:45]

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

[commit-bot: I haz the power, 2017-06-13 22:00:45]

Dry run: This issue passed the CQ dry run.

[dougt, 2017-06-14 03:42:27]

dougt@chromium.org changed reviewers:
+ dmazzoni@chromium.org

[dougt, 2017-06-14 03:42:27]

dmazzoni, ptal

[dmazzoni, 2017-06-15 06:26:00]

lgtm

[dougt, 2017-06-15 06:49:50]

The CQ bit was checked by dougt@chromium.org

[commit-bot: I haz the power, 2017-06-15 06:49:58]

CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-06-15 08:54:25]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1497509390305350, "parent_rev":
"6b583e8e663c6afb2a9ceffaaad6b54637bdd8fc", "commit_rev":
"4d2a90d730038e5608c9b89256746636b64b292f"}

[commit-bot: I haz the power, 2017-06-15 08:54:43]

Description was changed from

==========
Remove unused ui::AXPlatformNode pointer from BrowserAccessibility.

A while ago, we thought we would keep the the platform node as a seperate
object.  Most of this was removed in
https://codereview.chromium.org/2886353003 but we missed this.

BUG=703369
==========

to

==========
Remove unused ui::AXPlatformNode pointer from BrowserAccessibility.

A while ago, we thought we would keep the the platform node as a seperate
object.  Most of this was removed in
https://codereview.chromium.org/2886353003 but we missed this.

BUG=703369

Review-Url: https://codereview.chromium.org/2930413004
Cr-Commit-Position: refs/heads/master@{#479644}
Committed:
https://chromium.googlesource.com/chromium/src/+/4d2a90d730038e5608c9b8925674...
==========

[commit-bot: I haz the power, 2017-06-15 08:54:44]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/4d2a90d730038e5608c9b8925674...