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

chrome/android/java/src/org/chromium/chrome/browser/BluetoothChooserDialog.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.chrome.browser;
 
 import android.Manifest;
 import android.app.Activity;
+import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
-import android.content.pm.PackageManager;
+import android.content.IntentFilter;
+import android.location.LocationManager;
 import android.text.SpannableString;
 import android.text.TextUtils;
 import android.view.View;
 
 import org.chromium.base.VisibleForTesting;
 import org.chromium.base.annotations.CalledByNative;
 import org.chromium.chrome.R;
 import org.chromium.chrome.browser.omnibox.OmniboxUrlEmphasizer;
 import org.chromium.chrome.browser.profiles.Profile;
 import org.chromium.components.location.LocationUtils;
 import org.chromium.ui.base.WindowAndroid;
 import org.chromium.ui.text.NoUnderlineClickableSpan;
 import org.chromium.ui.text.SpanApplier;
 import org.chromium.ui.text.SpanApplier.SpanInfo;
 
 /**
  * A dialog for picking available Bluetooth devices. This dialog is shown when a website requests to
  * pair with a certain class of Bluetooth devices (e.g. through a bluetooth.requestDevice Javascript
  * call).
+ *
+ * The dialog is shown by create() or show(), and always runs finishDialog() as it's closing.
  */
 public class BluetoothChooserDialog
         implements ItemChooserDialog.ItemSelectedCallback, WindowAndroid.PermissionCallback {
     // These constants match BluetoothChooserAndroid::ShowDiscoveryState, and are used in
     // notifyDiscoveryState().
     static final int DISCOVERY_FAILED_TO_START = 0;
     static final int DISCOVERING = 1;
     static final int DISCOVERY_IDLE = 2;
 
     // Values passed to nativeOnDialogFinished:eventType, and only used in the native function.
@@ skipping 20 matching lines @@
 
     // A pointer back to the native part of the implementation for this dialog.
     long mNativeBluetoothChooserDialogPtr;
 
     // The type of link that is shown within the dialog.
     private enum LinkType {
         EXPLAIN_BLUETOOTH,
         ADAPTER_OFF,
         ADAPTER_OFF_HELP,
         REQUEST_LOCATION_PERMISSION,
+        REQUEST_LOCATION_SERVICES,
         NEED_LOCATION_PERMISSION_HELP,
         RESTART_SEARCH,
     }
 
     /**
      * Creates the BluetoothChooserDialog.
      */
     @VisibleForTesting
     BluetoothChooserDialog(WindowAndroid windowAndroid, String origin, int securityLevel,
             long nativeBluetoothChooserDialogPtr) {
@@ skipping 42 matching lines @@
                 mActivity.getString(R.string.bluetooth_not_seeing_it_idle_some_found),
                 new SpanInfo("<link1>", "</link1>",
                         new BluetoothClickableSpan(LinkType.EXPLAIN_BLUETOOTH, mActivity)),
                 new SpanInfo("<link2>", "</link2>",
                         new BluetoothClickableSpan(LinkType.RESTART_SEARCH, mActivity)));
 
         ItemChooserDialog.ItemChooserLabels labels =
                 new ItemChooserDialog.ItemChooserLabels(title, searching, noneFound,
                         statusIdleNoneFound, statusIdleSomeFound, positiveButton);
         mItemChooserDialog = new ItemChooserDialog(mActivity, this, labels);
+
+        mActivity.registerReceiver(mLocationModeBroadcastReceiver,
+                new IntentFilter(LocationManager.MODE_CHANGED_ACTION));
+    }
+
+    // Called to report the dialog's results back to native code.
+    private void finishDialog(int resultCode, String id) {
+        mActivity.unregisterReceiver(mLocationModeBroadcastReceiver);
+        if (mNativeBluetoothChooserDialogPtr != 0) {
+            nativeOnDialogFinished(mNativeBluetoothChooserDialogPtr, resultCode, id);
+        }
     }
 
     @Override
     public void onItemSelected(String id) {
-        if (mNativeBluetoothChooserDialogPtr != 0) {
-            if (id.isEmpty()) {
-                nativeOnDialogFinished(
-                        mNativeBluetoothChooserDialogPtr, DIALOG_FINISHED_CANCELLED, "");
-            } else {
-                nativeOnDialogFinished(
-                        mNativeBluetoothChooserDialogPtr, DIALOG_FINISHED_SELECTED, id);
-            }
+        if (id.isEmpty()) {
+            finishDialog(DIALOG_FINISHED_CANCELLED, "");
+        } else {
+            finishDialog(DIALOG_FINISHED_SELECTED, id);
         }
     }
 
     @Override
     public void onRequestPermissionsResult(String[] permissions, int[] grantResults) {
-        for (int i = 0; i < grantResults.length; i++) {
+        for (int i = 0; i < permissions.length; i++) {
             if (permissions[i].equals(Manifest.permission.ACCESS_COARSE_LOCATION)) {
-                if (grantResults[i] == PackageManager.PERMISSION_GRANTED) {
+                if (checkLocationServicesAndPermission()) {
                     mItemChooserDialog.clear();
                     nativeRestartSearch(mNativeBluetoothChooserDialogPtr);
-                } else {
-                    checkLocationPermission();
                 }
                 return;
             }
         }
         // If the location permission is not present, leave the currently-shown message in place.
     }
 
-    private void checkLocationPermission() {
-        if (LocationUtils.getInstance().hasAndroidLocationPermission(mActivity)) {
-            return;
+    @VisibleForTesting
+    final BroadcastReceiver mLocationModeBroadcastReceiver = new BroadcastReceiver() {
+        @Override
+        public void onReceive(Context context, Intent intent) {
+            if (LocationManager.MODE_CHANGED_ACTION.equals(intent.getAction())) {
+                if (checkLocationServicesAndPermission()) {
+                    mItemChooserDialog.clear();
+                    nativeRestartSearch(mNativeBluetoothChooserDialogPtr);
+                }
+            }
+        }
+    };
+
+    // Returns true if Location Services is on and Chrome has permission to see the user's location.
+    private boolean checkLocationServicesAndPermission() {
+        final boolean havePermission =
+                LocationUtils.getInstance().hasAndroidLocationPermission(mActivity);
+        final boolean locationServicesOn =
+                LocationUtils.getInstance().isSystemLocationSettingEnabled(mActivity);
+
+        if (!havePermission
+                && !mWindowAndroid.canRequestPermission(
+                           Manifest.permission.ACCESS_COARSE_LOCATION)) {
+            // Immediately close the dialog because the user has asked Chrome not to request the
+            // location permission.
+            finishDialog(DIALOG_FINISHED_DENIED_PERMISSION, "");
+            return false;
         }
 
-        if (!mWindowAndroid.canRequestPermission(Manifest.permission.ACCESS_COARSE_LOCATION)) {
-            if (mNativeBluetoothChooserDialogPtr != 0) {
-                nativeOnDialogFinished(
-                        mNativeBluetoothChooserDialogPtr, DIALOG_FINISHED_DENIED_PERMISSION, "");
-                return;
+        // Compute the message to show the user.
+        final SpanInfo permissionSpan = new SpanInfo("<permission_link>", "</permission_link>",
+                new BluetoothClickableSpan(LinkType.REQUEST_LOCATION_PERMISSION, mActivity));
+        final SpanInfo servicesSpan = new SpanInfo("<services_link>", "</services_link>",
+                new BluetoothClickableSpan(LinkType.REQUEST_LOCATION_SERVICES, mActivity));
+        final SpannableString needLocationMessage;
+        if (havePermission) {
+            if (locationServicesOn) {
+                // We don't need to request anything.
+                return true;
+            } else {
+                needLocationMessage = SpanApplier.applySpans(
+                        mActivity.getString(R.string.bluetooth_need_location_services_on),
+                        servicesSpan);
+            }
+        } else {
+            if (locationServicesOn) {
+                needLocationMessage = SpanApplier.applySpans(
+                        mActivity.getString(R.string.bluetooth_need_location_permission),
+                        permissionSpan);
+            } else {
+                needLocationMessage = SpanApplier.applySpans(
+                        mActivity.getString(
+                                R.string.bluetooth_need_location_permission_and_services_on),
+                        permissionSpan, servicesSpan);
             }
         }
 
-        SpannableString needLocationMessage = SpanApplier.applySpans(
-                mActivity.getString(R.string.bluetooth_need_location_permission),
-                new SpanInfo("<link>", "</link>",
-                        new BluetoothClickableSpan(
-                                     LinkType.REQUEST_LOCATION_PERMISSION, mActivity)));
-
         SpannableString needLocationStatus = SpanApplier.applySpans(
                 mActivity.getString(R.string.bluetooth_need_location_permission_help),
                 new SpanInfo("<link>", "</link>",
                         new BluetoothClickableSpan(
                                      LinkType.NEED_LOCATION_PERMISSION_HELP, mActivity)));
 
         mItemChooserDialog.setErrorState(needLocationMessage, needLocationStatus);
+        return false;
     }
 
     private class BluetoothClickableSpan extends NoUnderlineClickableSpan {
         // The type of link this span represents.
         private LinkType mLinkType;
 
         private Context mContext;
 
         BluetoothClickableSpan(LinkType linkType, Context context) {
             mLinkType = linkType;
@@ skipping 26 matching lines @@
                     nativeShowBluetoothAdapterOffLink(mNativeBluetoothChooserDialogPtr);
                     closeDialog();
                     break;
                 }
                 case REQUEST_LOCATION_PERMISSION: {
                     mWindowAndroid.requestPermissions(
                             new String[] {Manifest.permission.ACCESS_COARSE_LOCATION},
                             BluetoothChooserDialog.this);
                     break;
                 }
+                case REQUEST_LOCATION_SERVICES: {
+                    mContext.startActivity(
+                            LocationUtils.getInstance().getSystemLocationSettingsIntent());
+                    break;
+                }
                 case NEED_LOCATION_PERMISSION_HELP: {
                     nativeShowNeedLocationPermissionLink(mNativeBluetoothChooserDialogPtr);
                     closeDialog();
                     break;
                 }
                 case RESTART_SEARCH: {
                     mItemChooserDialog.clear();
                     nativeRestartSearch(mNativeBluetoothChooserDialogPtr);
                     break;
                 }
@@ skipping 64 matching lines @@
         if (mNativeBluetoothChooserDialogPtr != 0) {
             nativeRestartSearch(mNativeBluetoothChooserDialogPtr);
         }
     }
 
     @VisibleForTesting
     @CalledByNative
     void notifyDiscoveryState(int discoveryState) {
         switch (discoveryState) {
             case DISCOVERY_FAILED_TO_START: {
-                // FAILED_TO_START might be caused by a missing Location permission.
+                // FAILED_TO_START might be caused by a missing Location
+                // permission or by the Location service being turned off.
                 // Check, and show a request if so.
-                checkLocationPermission();
+                checkLocationServicesAndPermission();
                 break;
             }
             case DISCOVERY_IDLE: {
                 mItemChooserDialog.setIdleState();
                 break;
             }
             default: {
                 // TODO(jyasskin): Report the new state to the user.
                 break;
             }
         }
     }
 
     @VisibleForTesting
     native void nativeOnDialogFinished(
             long nativeBluetoothChooserAndroid, int eventType, String deviceId);
     @VisibleForTesting
     native void nativeRestartSearch(long nativeBluetoothChooserAndroid);
     // Help links.
     @VisibleForTesting
     native void nativeShowBluetoothOverviewLink(long nativeBluetoothChooserAndroid);
     @VisibleForTesting
     native void nativeShowBluetoothAdapterOffLink(long nativeBluetoothChooserAndroid);
     @VisibleForTesting
     native void nativeShowNeedLocationPermissionLink(long nativeBluetoothChooserAndroid);
 }