Fix ChromeVox's detection of whether the current document has focus.

Fix ChromeVox's detection of whether the current document has focus.

Added a new helper function to determine whether the document has focus,
taking into account whether an iframe or webview element has focus
and whether the document is hidden.

This fixes issues where there were two ChromeVox active indicators showing,
one on the outer frame and one inside the inner frame or webview. It also
fixes issues with other speech-generating events being processed in both
frames at once.

BUG=484904
Committed: https://crrev.com/28df096f78b61caa9fa43ae6794c89e2f6b01f82
Cr-Commit-Position: refs/heads/master@{#329956}

[dmazzoni, 2015-05-14 18:33:25]

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

[dmazzoni, 2015-05-14 18:35:40]

cc: glevin

[David Tseng, 2015-05-14 19:00:33]

lgtm

https://codereview.chromium.org/1137403003/diff/1/chrome/browser/resources/ch...
File
chrome/browser/resources/chromeos/chromevox/chromevox/injected/event_watcher.js
(right):

https://codereview.chromium.org/1137403003/diff/1/chrome/browser/resources/ch...
chrome/browser/resources/chromeos/chromevox/chromevox/injected/event_watcher.js:258:
// document isn't focused.
nit: D

[dmazzoni, 2015-05-14 22:27:09]

The CQ bit was checked by dmazzoni@chromium.org

[commit-bot: I haz the power, 2015-05-14 22:29:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1137403003/1

[commit-bot: I haz the power, 2015-05-14 22:36:19]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-14 22:37:08]

Patchset 1 (id:??) landed as
https://crrev.com/28df096f78b61caa9fa43ae6794c89e2f6b01f82
Cr-Commit-Position: refs/heads/master@{#329956}