Fix documentation in components/google/core/browser/google_url_tracker.h

The overridden method is from NetworkChangeObserver and not from
IPAddressObserver.

TBR=isherman@chromium.org

Bug: 754695
Change-Id: Ic37fccfce1abc1e89ad6300b652416cd73a6f39b
Reviewed-on: https://chromium-review.googlesource.com/749302Reviewed-by: Helen Li <xunjieli@chromium.org>
Commit-Queue: Helen Li <xunjieli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#513253}

components/google/core/browser/google_url_tracker.h

@@ -81,7 +81,7 @@ class GoogleURLTracker
   // net::URLFetcherDelegate:
   void OnURLFetchComplete(const net::URLFetcher* source) override;
 
-  // NetworkChangeNotifier::IPAddressObserver:
+  // NetworkChangeNotifier::NetworkChangeObserver:
   void OnNetworkChanged(
       net::NetworkChangeNotifier::ConnectionType type) override;