Add a GamepadVibration runtime feature flag

In previous versions, the vibration feature was enabled with the
GamepadExtensions runtime feature flag. This CL splits the vibration
functionality into a separate flag that is enabled by default. This
allows the vibration feature to be enabled independently of other
features that use the same runtime flag.

BUG=749295

Change-Id: Ia8017e8b0ecd9df4490e8b205ecd1f49509c687b
Reviewed-on: https://chromium-review.googlesource.com/1027996
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Commit-Queue: Matt Reynolds <mattreynolds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#555211}
14 files changed