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Since the observation of the local powered state change and the receiver of
enable/disable requests from Android is in arc_bluetooth_service are in
arc_setting_service and arc_bluetooth_bridge separately, the power state can
get out of sync or restore to the wrong state due to the lack of coordination
between these two pieces of information.

Issues:
- The powered state can get out-of-sync between Android and Chrome if the power
  state of adapter is repeatedly toggled from Chrome setting.
- If the powered state is ON before deep suspend/resume, the state will
  turn to OFF after resume and turn immediately back to ON on Chrome. However
  without waiting for the previous disable intent to finish, arc_setting_service
  sends the enable intent right after while Android Bluetooth statck is still
  processing the disable intent. Also there is a 3~4 seconds delay for bringing
  down to complete on Android Bluetooth stack. Besides, the enable intent
  is treated as a no op if the ongoing intent is disable. So after 3~4 seconds
  Android sends a disable request to Chrome while the powered state is ON on
  Chrome, so the powered state fall to the wrong one, disable, instead.

The changes includes:
 - moving the observation of Bluetooth adapter from arc_settings_service
   to arc_bluetooth_bridge,
 - changing the cycle of observing Bluetooth adapter from living along with ARC
   Bluetooth instance to living along with ARC Bluetooth bridge,
 - adding IntentHelperObserver to listen to the OnInstanceReady event and fire
   the initial powered state of Bluetooth to Android via intent,
 - adding two queues and a timer to track the powered state changes initiated by
   either Chrome or Android and to track the completion of the power
   changes initiated by Chrome,
 - and adding helper functions to enqueue/dequeue the power change intents and
   to compress the toggling of state to reduce the intents sent to Android.

BUG=b:62578573
TEST=(1) On Android start-up, verify that the powered state is synchronized
     between Android and Chrome.
     (2) After Repeatedly toggling Bluetooth powered state, the state
     remains synchronized between Android and Chrome.
     (3) Put device into deep suspend and resume, the state restores to
     the previous state.

Change-Id: I753839e2bb9228703492ebd23703cf8b67494998
Reviewed-on: https://chromium-review.googlesource.com/580314
Commit-Queue: Miao-chen Chou <mcchou@chromium.org>
Reviewed-by: Luis Hector Chavez <lhchavez@chromium.org>
Reviewed-by: Rahul Chaturvedi <rkc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491556}