Fix crash when accessing automation node from stale AX tree

Fix crash when accessing automation node from stale AX tree

The problem is that the root node of a stale AX tree computes its id
dynamically, but if that AX tree doesn't exist anymore it was returning
undefined, and then passing undefined to any of the native bindinds was a
fatal error.

The solution is just to return -1 instead of undefined as the id.

BUG=526255
Committed: https://crrev.com/ace50646dcd95261ef8e6aca2096458828532fbc
Cr-Commit-Position: refs/heads/master@{#346394}

[dmazzoni, 2015-08-28 20:14:54]

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

[David Tseng, 2015-08-28 21:57:28]

Thanks for the fix. Could we get a test for this?

[dmazzoni, 2015-08-28 22:38:32]

Done - modified an existing test so that it triggers the crash without this
patch.

[David Tseng, 2015-08-28 22:51:25]

lgtm

https://codereview.chromium.org/1308813008/diff/40001/chrome/test/data/extens...
File chrome/test/data/extensions/api_test/automation/tests/tabs/close_tab.js
(right):

https://codereview.chromium.org/1308813008/diff/40001/chrome/test/data/extens...
chrome/test/data/extensions/api_test/automation/tests/tabs/close_tab.js:11: //
Poll until the root node doesn't have a role anymore
Do we get an event (as to avoid busy waiting?).

[dmazzoni, 2015-08-28 23:02:36]

https://codereview.chromium.org/1308813008/diff/40001/chrome/test/data/extens...
File chrome/test/data/extensions/api_test/automation/tests/tabs/close_tab.js
(right):

https://codereview.chromium.org/1308813008/diff/40001/chrome/test/data/extens...
chrome/test/data/extensions/api_test/automation/tests/tabs/close_tab.js:11: //
Poll until the root node doesn't have a role anymore
On 2015/08/28 22:51:25, David Tseng wrote:
> Do we get an event (as to avoid busy waiting?).

We get the event immediately before it's destroyed - this is on purpose, so you
can figure out *what* got destroyed. So a setTimeout(0) would work in that
immediately afterwards, that node will be invalid.

I didn't want to depend on setTimeout(0), though, I thought it'd be more robust
to basically say the test busy-waits until the node becomes invalid (which it
should do quickly).

[dmazzoni, 2015-08-28 23:02:52]

The CQ bit was checked by dmazzoni@chromium.org

[commit-bot: I haz the power, 2015-08-28 23:05:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1308813008/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1308813008/40001

[commit-bot: I haz the power, 2015-08-29 00:24:52]

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

[commit-bot: I haz the power, 2015-08-29 00:24:52]

Try jobs failed on following builders:
  win_chromium_x64_rel_ng on tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_x64_...)

[dmazzoni, 2015-08-31 14:58:59]

The CQ bit was checked by dmazzoni@chromium.org

[commit-bot: I haz the power, 2015-08-31 14:59:24]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1308813008/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1308813008/40001

[commit-bot: I haz the power, 2015-08-31 16:15:36]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-08-31 16:16:11]

Patchset 3 (id:??) landed as
https://crrev.com/ace50646dcd95261ef8e6aca2096458828532fbc
Cr-Commit-Position: refs/heads/master@{#346394}