shill: Use SuspendDone signal instead of PowerStateChanged.

PowerStateChanged will be removed from powerd soon; clients
should use SuspendImminent and SuspendDone instead.

Also simplify the interface exposed by PowerManager for
adding and removing suspend delays.

BUG=chromium:359619
TEST=updated tests

Change-Id: I7f96774570170591c2e5944245c368e165aaf972
Reviewed-on: https://chromium-review.googlesource.com/195690
Reviewed-by: Daniel Erat <derat@chromium.org>
Tested-by: Daniel Erat <derat@chromium.org>
Commit-Queue: Daniel Erat <derat@chromium.org>
diff --git a/metrics.h b/metrics.h
index ba1d36c..f0f9459 100644
--- a/metrics.h
+++ b/metrics.h
@@ -518,8 +518,8 @@
   void NotifySignalAtDisconnect(const Service &service,
                                 int16_t signal_strength);
 
-  // Notifies this object of a power management state change.
-  void NotifyPowerStateChange(PowerManager::SuspendState new_state);
+  // Notifies this object of the end of a suspend attempt.
+  void NotifySuspendDone();
 
   // Notifies this object that termination actions started executing.
   void NotifyTerminationActionsStarted(TerminationActionReason reason);