Record metrics for connected gamepads

Update the Gamepad.ConnectedDevice histogram when a device is
connected with a vendor and product ID pair matching a known
USB or Bluetooth gaming peripheral.

If the connected device is not recognized as a known gamepad, the
ID is not recorded. If the data fetcher that enumerated the
device has an independent means of verifying whether a device is
a gamepad, record an enum representing the data fetcher to the
Gamepad.UnknownGamepad histogram.

BUG=786250

Change-Id: I7e7797ee1e99b2076aa331ee9e589d157016993b
Reviewed-on: https://chromium-review.googlesource.com/c/1299543
Commit-Queue: Matt Reynolds <mattreynolds@chromium.org>
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616905}
11 files changed