Ensure there's no layout pending before accessing WebAXObject from TestRunner.

Ensure there's no layout pending before accessing WebAXObject from TestRunner.

It's not safe to call WebAXObject functions when there's a layout pending.
Chrome never does this, it only calls WebAXObject from
renderer_accessibility_complete, and it makes sure to update layout before
accessing the accessibility tree.

TestRunner didn't have the same protections, so this just explicitly updates
the layout before any accessibility call.

BUG=393829
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=289489

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=290880

[dmazzoni, 2014-08-13 19:24:41]

The test is in https://codereview.chromium.org/465143003

[dglazkov, 2014-08-13 22:39:02]

lgtm

[dmazzoni, 2014-08-13 22:58:32]

The CQ bit was checked by dmazzoni@chromium.org

[commit-bot: I haz the power, 2014-08-13 23:00:56]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/dmazzoni@chromium.org/469803003/1

[commit-bot: I haz the power, 2014-08-14 08:11:24]

Committed patchset #1 (1) as 289489

[dmazzoni, 2014-08-20 17:27:20]

Re-landing after fixing flaky layout test that failed after the first time I
tried to land this.

[dmazzoni, 2014-08-20 17:27:24]

The CQ bit was checked by dmazzoni@chromium.org

[commit-bot: I haz the power, 2014-08-20 17:28:20]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/dmazzoni@chromium.org/469803003/1

[commit-bot: I haz the power, 2014-08-20 18:59:54]

Committed patchset #1 (1) as 290880