Add UseCounters for alert(), confirm() and prompt() usage against site engagement.

Add UseCounters for alert(), confirm() and prompt() usage against site engagement.

These UseCounters will allow an investigation into how often alert(),
confirm(), and prompt() are called for sites with different engagement
levels.

BUG=644268
Review-Url: https://codereview.chromium.org/2610813006
Cr-Commit-Position: refs/heads/master@{#441875}
Committed: https://chromium.googlesource.com/chromium/src/+/d6dfbbf145c5977edd5d53c056856286506a7434

[dominickn, 2017-01-06 02:39:23]

The CQ bit was checked by dominickn@chromium.org to run a CQ dry run

[dominickn, 2017-01-06 02:39:44]

dominickn@chromium.org changed reviewers:
+ haraken@chromium.org

[dominickn, 2017-01-06 02:39:44]

PTAL, thanks!

[commit-bot: I haz the power, 2017-01-06 02:39:57]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[haraken, 2017-01-06 02:47:24]

LGTM

[commit-bot: I haz the power, 2017-01-06 04:42:39]

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

[commit-bot: I haz the power, 2017-01-06 04:42:40]

Dry run: This issue passed the CQ dry run.

[dominickn, 2017-01-06 04:43:25]

The CQ bit was checked by dominickn@chromium.org

[commit-bot: I haz the power, 2017-01-06 04:43:43]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-01-06 04:48:58]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1483677805641640, "parent_rev":
"3b8662f8f863dee29b406e73ce7aa7ad22adad4e", "commit_rev":
"d6dfbbf145c5977edd5d53c056856286506a7434"}

[commit-bot: I haz the power, 2017-01-06 04:49:29]

Description was changed from

==========
Add UseCounters for alert(), confirm() and prompt() usage against site
engagement.

These UseCounters will allow an investigation into how often alert(),
confirm(), and prompt() are called for sites with different engagement
levels.

BUG=644268
==========

to

==========
Add UseCounters for alert(), confirm() and prompt() usage against site
engagement.

These UseCounters will allow an investigation into how often alert(),
confirm(), and prompt() are called for sites with different engagement
levels.

BUG=644268

Review-Url: https://codereview.chromium.org/2610813006
Cr-Commit-Position: refs/heads/master@{#441875}
Committed:
https://chromium.googlesource.com/chromium/src/+/d6dfbbf145c5977edd5d53c05685...
==========

[commit-bot: I haz the power, 2017-01-06 04:49:30]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/d6dfbbf145c5977edd5d53c05685...