bluetooth: android: register for adapter on/off events.

device/bluetooth/bluetooth_adapter_android.h

Index: device/bluetooth/bluetooth_adapter_android.h
diff --git a/device/bluetooth/bluetooth_adapter_android.h b/device/bluetooth/bluetooth_adapter_android.h
index 3612602c639e8ed1c99b7227d558eca6842228f5..8ebb49ce13188a3bc763c83498962d9d2c71a982 100644
--- a/device/bluetooth/bluetooth_adapter_android.h
+++ b/device/bluetooth/bluetooth_adapter_android.h
@@ -83,6 +83,11 @@ class DEVICE_BLUETOOTH_EXPORT BluetoothAdapterAndroid final
       const CreateAdvertisementCallback& callback,
       const CreateAdvertisementErrorCallback& error_callback) override;
 
+  // Called when adapter state changes.
+  void OnAdapterStateChanged(JNIEnv* env,
+                             const base::android::JavaParamRef<jobject>& caller,
+                             const bool powered);
+
   // Handles a scan error event by invalidating all discovery sessions.
   void OnScanFailed(JNIEnv* env,
                     const base::android::JavaParamRef<jobject>& caller);