This CL includes an implementation of the Wake Lock spec after
https://github.com/w3c/wake-lock/pull/201 and subsequent pull requests that
clear up a few points.

Specifically, this CL implements the Wake Lock spec at commit
9a17e1f48ca519090b82dddca09ace3e1773931c ('Explain why WakeLock.request()
has no "if aborted" step').

The spec has undergone significant changes since the latest update to the
implementation, and multiple features were added and removed to the spec in
the meantime.

From a Web API user perspective, the Wake Lock API surface is now pretty
small:
* While the Wake Lock interface still exists, it only contains two static
  methods, requestPermission() and request(). requestPermission() needs
  pending work on the permissions side in //content and //chrome, so this CL
  only implements request().
* navigator.getWakeLock() and WakeLock.createRequest() have been removed and
  replaced by a single call to WakeLock.request().
* A consequence of the two items above is that it is no longer possible to
  actually hold a WakeLock object (and all attributes and event listeners
  are gone).
* WakeLock.request() returns a promise that never resolves when it works,
  and rejects with either NotAllowedError or AbortError in case something
  did not work or the lock was cancelled.
* We now use the AbortSignal mechanism from the DOM spec (just like other
  specs such as Fetch) for cancelling a Wake Lock.

From a Blink perspective:
* wake_lock.cc just performs the validation steps in WakeLock.request(), and
  delegates the act of acquiring or releasing a wake lock to
  WakeLockController.
* WakeLockController is similar to other controllers (like the ones in
  device_orientation/) and tracks per-Document wake lock state. It also does
  not acquire or release wake locks itself, but rather delegates it to its
  per-wake-lock-type instances of WakeLockStateRecord. It also handles
  per-document visibility and activity changes.
* WakeLockStateRecord implements the spec's concept of "state record" and
  actually requests and cancels wake locks (by talking to //content and
  //services).

Major pending Wake Lock features present in the spec:
* Workers support
* Permission handling

Bug: 257511
Change-Id: I3dced3a16711b720a96b1a0d5c008d49e3b38c6d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1605687
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Bo <boliu@chromium.org>
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Commit-Queue: Raphael Kubo da Costa <raphael.kubo.da.costa@intel.com>
Cr-Commit-Position: refs/heads/master@{#663207}