Remove owned views from AXAuraObjCache when widget is deleted.

Remove owned views from AXAuraObjCache when widget is deleted.

A follow-up change should notify automation clients, too.
Even then, a CHECK() that an AX obj wrapper exists for a given ID doesn't
make sense because the IPC could have been received after an object was
deleted but before the client was informed of it.

BUG=514728
Committed: https://crrev.com/9febb059904b30661543102a540cf8ae00a78cae
Cr-Commit-Position: refs/heads/master@{#343061}

[dmazzoni, 2015-08-10 19:37:10]

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

[David Tseng, 2015-08-10 20:38:25]

lgtm

[dmazzoni, 2015-08-10 21:53:03]

The CQ bit was checked by dmazzoni@chromium.org

[commit-bot: I haz the power, 2015-08-10 21:53:48]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1283593006/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1283593006/1

[commit-bot: I haz the power, 2015-08-10 22:35:17]

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

[commit-bot: I haz the power, 2015-08-10 22:35:18]

Try jobs failed on following builders:
  linux_chromium_chromeos_ozone_rel_ng on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[dmazzoni, 2015-08-12 17:48:54]

The CQ bit was checked by dmazzoni@chromium.org

[dmazzoni, 2015-08-12 17:48:55]

The patchset sent to the CQ was uploaded after l-g-t-m from dtseng@chromium.org
Link to the patchset: https://codereview.chromium.org/1283593006/#ps20001
(title: "nullptr check")

[commit-bot: I haz the power, 2015-08-12 17:49:38]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1283593006/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1283593006/20001

[commit-bot: I haz the power, 2015-08-12 18:33:33]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-08-12 18:33:58]

Patchset 2 (id:??) landed as
https://crrev.com/9febb059904b30661543102a540cf8ae00a78cae
Cr-Commit-Position: refs/heads/master@{#343061}