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

Index: chrome/android/java/src/org/chromium/chrome/browser/BluetoothChooserDialog.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/BluetoothChooserDialog.java b/chrome/android/java/src/org/chromium/chrome/browser/BluetoothChooserDialog.java
index df15c1638c115883800da2309259c17a7c314a7d..83fa3b72047a2a21562f4328744244f8eda9adfe 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/BluetoothChooserDialog.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/BluetoothChooserDialog.java
@@ -6,9 +6,11 @@ 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;
@@ -28,6 +30,8 @@ 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 {
@@ -62,12 +66,27 @@ public class BluetoothChooserDialog
     // A pointer back to the native part of the implementation for this dialog.
     long mNativeBluetoothChooserDialogPtr;
 
+    @VisibleForTesting
+    final BroadcastReceiver mLocationModeBroadcastReceiver = new BroadcastReceiver() {
+        @Override
+        public void onReceive(Context context, Intent intent) {
+            if (!LocationManager.MODE_CHANGED_ACTION.equals(intent.getAction())) {
+                return;
+            }
+            if (checkLocationServicesAndPermission()) {
+                mItemChooserDialog.clear();
+                nativeRestartSearch(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,
     }
@@ -130,30 +149,35 @@ public class BluetoothChooserDialog
                 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;
             }
@@ -161,25 +185,50 @@ public class BluetoothChooserDialog
         // If the location permission is not present, leave the currently-shown message in place.
     }
 
-    private void checkLocationPermission() {
-        if (LocationUtils.getInstance().hasAndroidLocationPermission(mActivity)) {
-            return;
+    // 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>",
@@ -187,6 +236,7 @@ public class BluetoothChooserDialog
                                      LinkType.NEED_LOCATION_PERMISSION_HELP, mActivity)));
 
         mItemChooserDialog.setErrorState(needLocationMessage, needLocationStatus);
+        return false;
     }
 
     private class BluetoothClickableSpan extends NoUnderlineClickableSpan {
@@ -233,6 +283,11 @@ public class BluetoothChooserDialog
                             BluetoothChooserDialog.this);
                     break;
                 }
+                case REQUEST_LOCATION_SERVICES: {
+                    mContext.startActivity(
+                            LocationUtils.getInstance().getSystemLocationSettingsIntent());
+                    break;
+                }
                 case NEED_LOCATION_PERMISSION_HELP: {
                     nativeShowNeedLocationPermissionLink(mNativeBluetoothChooserDialogPtr);
                     closeDialog();
@@ -314,9 +369,10 @@ public class BluetoothChooserDialog
     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: {