Ship WebUSB

This change ends the WebUSB Origin Trial and enables the feature by
default.

Intent to Ship thread:
https://groups.google.com/a/chromium.org/d/msg/blink-dev/KuXx_k2KIis/-g-75FScBgAJ

Bug: 492204
Change-Id: I8af69ccd39c9eb0d7200f0fb25566ad189d5f42e
Reviewed-on: https://chromium-review.googlesource.com/513366
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Reviewed-by: Vincent Scheib <scheib@chromium.org>
Commit-Queue: Reilly Grant <reillyg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#476267}
21 files changed