Add WebUsbAllowDevicesForUrls policy

This change adds a new policy template for WebUsbAllowDevicesForUrls.
The new policy will allow a list of devices to be automatically granted
permission to be used for a list of URL patterns. This change also adds
a policy handler to validate the policy value and add the validated
value to Preferences using the pref name defined for this policy.

The design document for the new WebUSB policy is located at:

Bug: 854329
Change-Id: I03657906834ba12f43735d7339a8ca404dc50718
Commit-Queue: Ovidio Henriquez <>
Reviewed-by: Jochen Eisinger <>
Reviewed-by: Sergey Poromov <>
Cr-Commit-Position: refs/heads/master@{#595880}
12 files changed