Revert of Remove WindowFocusAllowedIndicator and associated code.

Revert of Remove WindowFocusAllowedIndicator and associated code. (patchset #2 id:20001 of https://codereview.chromium.org/722423004/)

Reason for revert:
Crashing, see bug 441968

Original issue's description:
> Remove WindowFocusAllowedIndicator and associated code.
> 
> This is the last part of a three-sided CL:
> Part 1: https://codereview.chromium.org/777483004/
> Part 2: https://codereview.chromium.org/786403003/
> Part 3: <this>
> 
> BUG=440740
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=187135

TBR=jochen@chromium.org,mkwst@chromium.org,mlamouri@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=440740
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=187186

[amineer_google, 2014-12-15 22:47:56]

Created Revert of Remove WindowFocusAllowedIndicator and associated code.

[commit-bot: I haz the power, 2014-12-15 22:49:12]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/808563003/1

[commit-bot: I haz the power, 2014-12-15 22:49:13]

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

[commit-bot: I haz the power, 2014-12-15 22:49:14]

No LGTM from a valid reviewer yet. Only full committers are accepted.
Even if an LGTM may have been provided, it was from a non-committer,
_not_ a full super star committer.
See http://www.chromium.org/getting-involved/become-a-committer
Note that this has nothing to do with OWNERS files.

[Ken Rockot(use gerrit already), 2014-12-15 22:50:22]

On 2014/12/15 22:49:14, I haz the power (commit-bot) wrote:
> No LGTM from a valid reviewer yet. Only full committers are accepted.
> Even if an LGTM may have been provided, it was from a non-committer,
> _not_ a full super star committer.
> See http://www.chromium.org/getting-involved/become-a-committer
> Note that this has nothing to do with OWNERS files.

lgtm

[amineer_google, 2014-12-15 22:53:07]

The CQ bit was checked by amineer@google.com

[commit-bot: I haz the power, 2014-12-15 22:54:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/808563003/1

[commit-bot: I haz the power, 2014-12-15 22:55:28]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=187186