Speculatively fix OSX crashes involving service removal

chrome/browser/local_discovery/service_discovery_client_mac.mm

 // 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.
 
 #include "chrome/browser/local_discovery/service_discovery_client_mac.h"
 
 #import <Foundation/Foundation.h>
 #import <arpa/inet.h>
 #import <net/if_dl.h>
 
@@ skipping 413 matching lines @@
   [netService startMonitoring];
   [services_ addObject:netService];
 
   container_->OnServicesUpdate(local_discovery::ServiceWatcher::UPDATE_ADDED,
                                [[netService name] UTF8String]);
 }
 
 - (void)netServiceBrowser:(NSNetServiceBrowser *)netServiceBrowser
         didRemoveService:(NSNetService *)netService
         moreComing:(BOOL)moreServicesComing {
-  container_->OnServicesUpdate(local_discovery::ServiceWatcher::UPDATE_REMOVED,
-                               [[netService name] UTF8String]);
-
   NSUInteger index = [services_ indexOfObject:netService];
   if (index != NSNotFound) {
+    container_->OnServicesUpdate(
+        local_discovery::ServiceWatcher::UPDATE_REMOVED,
+        [[netService name] UTF8String]);
+
     // Stop monitoring this service for updates.
     [[services_ objectAtIndex:index] stopMonitoring];
     [services_ removeObjectAtIndex:index];
   }
 }
 
 - (void)netService:(NSNetService *)sender
         didUpdateTXTRecordData:(NSData *)data {
   container_->OnServicesUpdate(local_discovery::ServiceWatcher::UPDATE_CHANGED,
                                [[sender name] UTF8String]);
@@ skipping 15 matching lines @@
   container_->OnResolveUpdate(local_discovery::ServiceResolver::STATUS_SUCCESS);
 }
 
 - (void)netService:(NSNetService *)sender
         didNotResolve:(NSDictionary *)errorDict {
   container_->OnResolveUpdate(
       local_discovery::ServiceResolver::STATUS_REQUEST_TIMEOUT);
 }
 
 @end