Work around <webview> focus bugs by enforcing focus event invariants.

Work around <webview> focus bugs by enforcing focus eventinvariants.

Workarounds are necessary due to webview firing events out of order. Example, a focus event gets fired on a descendant then the root of the webview when entering the webview via tab key. Similarly, tabbing out of the webview causes a focus event on the root as well.

This cl depends on a Blink change to fire blur events to accurately report focus state.

Invariants:
- the root of the focus target should have focused state set to true (except for nodes with the root as desktop, which is implicitly always focused).
- embedded objects should never be focused (even though webview fires focus events on them)
- a sequence of focus events like
focus event: root.firstChild
focus event: root
should result in ChromeVox focus remaining on root.firstChild

TEST=Tab/shift tab behaves correctly on GAIA sign in page.
BUG=534619, 525643
Committed: https://crrev.com/d336af2c96432f9c8d4b55faa3646c78c14607c7
Cr-Commit-Position: refs/heads/master@{#352127}

[David Tseng, 2015-09-22 15:55:41]

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

[David Tseng, 2015-09-22 15:55:48]



[Fady Samuel, 2015-09-22 15:57:19]

On 2015/09/22 15:55:48, David Tseng wrote:
> 

Please file a bug and assign to lazyboy@ to fix the webview issue.

[David Tseng, 2015-09-29 22:04:19]

On 2015/09/22 15:57:19, Fady Samuel wrote:
> On 2015/09/22 15:55:48, David Tseng wrote:
> > 
> 
> Please file a bug and assign to lazyboy@ to fix the webview issue.

I filed crbug.com/537413 and assigned to dmazzoni@ for now to triage. I believe
it's accessibility specific.

[David Tseng, 2015-09-30 16:36:55]

On 2015/09/29 22:04:19, David Tseng wrote:
> On 2015/09/22 15:57:19, Fady Samuel wrote:
> > On 2015/09/22 15:55:48, David Tseng wrote:
> > > 
> > 
> > Please file a bug and assign to lazyboy@ to fix the webview issue.
> 
> I filed crbug.com/537413 and assigned to dmazzoni@ for now to triage. I
believe
> it's accessibility specific.

Friendly ping dmazzoni@ before we figure out the webview issues. Thanks.

[dmazzoni, 2015-09-30 16:39:49]

lgtm as a temporary workaround. I hope to have a cleaner solution soon, waiting
on the review of a changelist it depends on still.

[David Tseng, 2015-09-30 16:40:23]

The CQ bit was checked by dtseng@chromium.org

[commit-bot: I haz the power, 2015-09-30 16:40:46]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1361633003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1361633003/1

[commit-bot: I haz the power, 2015-09-30 17:25:38]

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

[commit-bot: I haz the power, 2015-09-30 17:25:39]

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_...)

[David Tseng, 2015-10-02 20:56:33]

The CQ bit was checked by dtseng@chromium.org

[David Tseng, 2015-10-02 20:56:33]

The patchset sent to the CQ was uploaded after l-g-t-m from
dmazzoni@chromium.org
Link to the patchset: https://codereview.chromium.org/1361633003/#ps20001
(title: " ")

[commit-bot: I haz the power, 2015-10-02 20:59:33]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1361633003/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1361633003/20001

[commit-bot: I haz the power, 2015-10-02 21:06:55]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-10-02 21:07:45]

Patchset 2 (id:??) landed as
https://crrev.com/d336af2c96432f9c8d4b55faa3646c78c14607c7
Cr-Commit-Position: refs/heads/master@{#352127}