arc-bridge: Remove unused PowerObserver

components/arc/arc_bridge_service.h

Index: components/arc/arc_bridge_service.h
diff --git a/components/arc/arc_bridge_service.h b/components/arc/arc_bridge_service.h
index 12aae9d30f76d063bda8a67dfb05e6add5973802..6e8c885b7f6508e7438e6a5ec457eacd53824a4f 100644
--- a/components/arc/arc_bridge_service.h
+++ b/components/arc/arc_bridge_service.h
@@ -95,19 +95,6 @@ class ArcBridgeService : public ArcBridgeHost {
     virtual ~Observer() {}
   };
 
-  // Notifies power management-related events.
-  class PowerObserver {
-   public:
-    // Called whenever ARC requests a wake lock.
-    virtual void OnAcquireDisplayWakeLock(DisplayWakeLockType type) {}
-
-    // Called whenever ARC releases a wake lock.
-    virtual void OnReleaseDisplayWakeLock(DisplayWakeLockType type) {}
-
-   protected:
-    virtual ~PowerObserver() {}
-  };
-
   ~ArcBridgeService() override;
 
   // Gets the global instance of the ARC Bridge Service. This can only be