Fix some grammar in content/browser/geolocation/

content/browser/geolocation/core_location_data_provider_mac.mm

 // Copyright (c) 2011 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.
 
 // This file contains the class definitions for the CoreLocation data provider
 // class and the accompanying Objective C wrapper class. This data provider
 // is used to allow the CoreLocation wrapper to run on the UI thread, since
 // CLLocationManager's start and stop updating methods must be called from a
 // thread with an active NSRunLoop.  Currently only the UI thread appears to
 // fill that requirement.
@@ skipping 64 matching lines @@
   NSBundle* bundle_;
   Class locationManagerClass_;
   id locationManager_;
   CoreLocationDataProviderMac* dataProvider_;
 }
 
 - (id)initWithDataProvider:(CoreLocationDataProviderMac*)dataProvider;
 - (void)dealloc;
 
 // Can be called from any thread since it does not require an NSRunLoop. However
-// it is not threadsafe to receive concurrent calls until after it's first
+// it is not threadsafe to receive concurrent calls until after a first
 // successful call (to avoid |bundle_| being double initialized)
 - (BOOL)locationDataAvailable;
 
 // These should always be called from BrowserThread::UI
 - (void)startLocation;
 - (void)stopLocation;
 
 // These should only be called by CLLocationManager
 - (void)locationManager:(CLLocationManager*)manager
     didUpdateToLocation:(CLLocation*)newLocation
@@ skipping 145 matching lines @@
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   [wrapper_ stopLocation];
 }
 
 void CoreLocationDataProviderMac::PositionUpdated(Geoposition position) {
   DCHECK(MessageLoop::current() ==
          GeolocationProvider::GetInstance()->message_loop());
   if (provider_)
     provider_->SetPosition(&position);
 }