If location services are turned off, have the BT chooser prompt the user to turn them on.

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;
 import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
+import android.location.LocationManager;
 import android.os.Build;
 import android.os.ParcelUuid;
 
 import org.chromium.base.Log;
 import org.chromium.base.annotations.CalledByNative;
 import org.chromium.base.annotations.JNINamespace;
 
 import java.util.List;
 
 /**
@@ skipping 154 matching lines @@
         }
 
         Log.d(TAG, "removeDiscoverySession: Now %d sessions.", mNumDiscoverySessions);
         return true;
     }
 
     // ---------------------------------------------------------------------------------------------
     // Implementation details:
 
     /**
-     * @return true if Chromium has permission to scan for Bluetooth devices.
+     * @return true if Chromium has permission to scan for Bluetooth devices and location services
+     * are on.
      */
     private boolean canScan() {
         Wrappers.ContextWrapper context = mAdapter.getContext();
-        return context.checkPermission(Manifest.permission.ACCESS_COARSE_LOCATION)
+        boolean havePermission = context.checkPermission(Manifest.permission.ACCESS_COARSE_LOCATION)
                 || context.checkPermission(Manifest.permission.ACCESS_FINE_LOCATION);
+
+        Wrappers.LocationManagerWrapper locationManager = context.getLocationManager();
+        boolean locationServicesOn =
+                locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER)

[Jeffrey Yasskin, 2016/06/03 01:52:48]

https://developer.android.com/reference/android/location/LocationManager.html...
recommends using Settings.Secure.getInt(LOCATION_MODE), but Chrome has 3 uses of
isProviderEnabled() vs 1 use of getInt(LOCATION_MODE). Which should we be using
in general?

+                || locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
+
+        return havePermission && locationServicesOn;
     }
 
     private void registerBroadcastReceiver() {
         if (mAdapter != null) {
             mAdapter.getContext().registerReceiver(
                     this, new IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED));
         }
     }
 
     private void unregisterBroadcastReceiver() {
@@ skipping 139 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);
 }