Convert //extensions/power_api to be client of wake lock interface.

Wake Lock is a Mojo interface that wraps PowerSaveBlocker. As part of the
creation of standalone Device Service, all browser-side clients of
PowerSaveBlocker should be converted to be clients of the Wake Lock Mojo
interface instead.

Adds the "ChangeType()" in WakeLock mojo interfaces to meet the scenario
of PowerAPI usage. Unittest of wake lock is modified accordingly.

BUG=689421

Change-Id: Ic73852d87bd32543cf959ca9957223da7bae4966
Reviewed-on: https://chromium-review.googlesource.com/539655
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Colin Blundell <blundell@chromium.org>
Commit-Queue: Ke He <ke.he@intel.com>
Cr-Commit-Position: refs/heads/master@{#482135}
20 files changed