GeoLocation: add support for GmsCore location provider

device/geolocation/android/java/src/org/chromium/device/geolocation/LocationProviderFactory.java

 // Copyright 2013 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.geolocation;
 
 import android.content.Context;
 
 import org.chromium.base.VisibleForTesting;
 
 /**
- * Factory to create a LocationProvider to allow us to inject
- * a mock for tests.
+ * Factory to create a LocationProvider to allow us to inject a mock for tests.
  */
 public class LocationProviderFactory {
     private static LocationProviderFactory.LocationProvider sProviderImpl;
 
     /**
      * LocationProviderFactory.create() returns an instance of this interface.
      */
     public interface LocationProvider {
         /**
-         * Start listening for location updates.
-         * @param enableHighAccuracy Whether or not to enable high accuracy location providers.
+         * Start listening for location updates. Calling several times before stop() is interpreted
+         * as restart.
+         * @param enableHighAccuracy Whether or not to enable high accuracy location.
          */
         public void start(boolean enableHighAccuracy);
 
         /**
          * Stop listening for location updates.
          */
         public void stop();
 
         /**
          * Returns true if we are currently listening for location updates, false if not.
          */
         public boolean isRunning();
     }
 
     private LocationProviderFactory() {}
 
     @VisibleForTesting
     public static void setLocationProviderImpl(LocationProviderFactory.LocationProvider provider) {
-        assert sProviderImpl == null;
         sProviderImpl = provider;
     }
 
     public static LocationProvider create(Context context) {
-        if (sProviderImpl == null) {
+        if (sProviderImpl != null) return sProviderImpl;
+
+        if (LocationProviderGmsCore.isGooglePlayServicesAvailable(context)) {
+            sProviderImpl = new LocationProviderGmsCore(context);

[sgurun-gerrit only, 2017/04/26 22:22:54]

instead of doing this, can you set sProviderImpl from chrome? this way WebView
will continue to use LocationProviderAndroid

+        } else {
             sProviderImpl = new LocationProviderAndroid(context);
         }
         return sProviderImpl;
     }
 }