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

device/bluetooth/android/java/src/org/chromium/device/bluetooth/ChromeBluetoothAdapter.java

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.device.bluetooth;
 
 import android.Manifest;
 import android.annotation.TargetApi;
 import android.bluetooth.BluetoothAdapter;
 import android.bluetooth.le.ScanSettings;
@@ skipping 16 matching lines @@
  * device::BluetoothAdapter.
  *
  * Lifetime is controlled by device::BluetoothAdapterAndroid.
  */
 @JNINamespace("device")
 @TargetApi(Build.VERSION_CODES.LOLLIPOP)
 final class ChromeBluetoothAdapter extends BroadcastReceiver {
     private static final String TAG = "Bluetooth";
 
     private long mNativeBluetoothAdapterAndroid;
-    private Wrappers.BluetoothAdapterWrapper mAdapter;
+    // mAdapter is final to ensure registerReceiver is followed by unregisterReceiver.
+    private final Wrappers.BluetoothAdapterWrapper mAdapter;
     private int mNumDiscoverySessions;
     private ScanCallback mScanCallback;
 
     // ---------------------------------------------------------------------------------------------
     // Construction and handler for C++ object destruction.
 
     /**
      * Constructs a ChromeBluetoothAdapter.
      * @param nativeBluetoothAdapterAndroid Is the associated C++
      *                                      BluetoothAdapterAndroid pointer value.
@@ skipping 295 matching lines @@
     // 'Object' type must be used for |bluetoothDeviceWrapper| because inner class
     // Wrappers.BluetoothDeviceWrapper reference is not handled by jni_generator.py JavaToJni.
     // http://crbug.com/505554
     private native void nativeCreateOrUpdateDeviceOnScan(long nativeBluetoothAdapterAndroid,
             String address, Object bluetoothDeviceWrapper, List<ParcelUuid> advertisedUuids);
 
     // Binds to BluetoothAdapterAndroid::nativeOnAdapterStateChanged
     private native void nativeOnAdapterStateChanged(
             long nativeBluetoothAdapterAndroid, boolean powered);
 }