Adding ArcBridge interface for synchronizing brightness settings

components/arc/power/arc_power_bridge.h

Index: components/arc/power/arc_power_bridge.h
diff --git a/components/arc/power/arc_power_bridge.h b/components/arc/power/arc_power_bridge.h
index c459cffbb07d22b9066368ff692ff99dfba014c3..fbecdb138602b8408c5b800eb7947faf0fb6d650 100644
--- a/components/arc/power/arc_power_bridge.h
+++ b/components/arc/power/arc_power_bridge.h
@@ -41,10 +41,14 @@ class ArcPowerBridge : public ArcService,
   // DisplayConfigurator::Observer overrides.
   void OnPowerStateChanged(chromeos::DisplayPowerState power_state) override;
 
+  // PowerManagerClient::Observer overrides.
+  void BrightnessChanged(int level, bool user_initiated) override;
+
   // mojom::PowerHost overrides.
   void OnAcquireDisplayWakeLock(mojom::DisplayWakeLockType type) override;
   void OnReleaseDisplayWakeLock(mojom::DisplayWakeLockType type) override;
   void IsDisplayOn(const IsDisplayOnCallback& callback) override;
+  void SetBrightness(int32_t brightness) override;
 
  private:
   void ReleaseAllDisplayWakeLocks();