Merge WebUSB notification flag into experimental web platform features.

Merge WebUSB notification flag into experimental web platform features.

The WebUSB notification flag tells Chrome to scan for WebUSB-enabled
devices when they are connected to the system. This patch will expose
this code to a larger population to make sure that such scanning does
not introduce new crashes and reduce the number of flags developers must
enable to try out WebUSB.

BUG=492204
Committed: https://crrev.com/d58e643f244fea3c9ab3a03d306414cbf48b5a20
Cr-Commit-Position: refs/heads/master@{#357639}

[Reilly Grant (use Gerrit), 2015-10-30 22:37:08]

reillyg@chromium.org changed reviewers:
+ jochen@chromium.org

[Reilly Grant (use Gerrit), 2015-10-30 22:37:08]

Please take a look.

[jochen (gone - plz use gerrit), 2015-11-03 07:16:46]

lgtm

[Reilly Grant (use Gerrit), 2015-11-03 20:11:19]

The CQ bit was checked by reillyg@chromium.org

[commit-bot: I haz the power, 2015-11-03 20:14:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1426583008/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1426583008/1

[commit-bot: I haz the power, 2015-11-03 21:43:31]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-03 21:45:13]

Patchset 1 (id:??) landed as
https://crrev.com/d58e643f244fea3c9ab3a03d306414cbf48b5a20
Cr-Commit-Position: refs/heads/master@{#357639}