Add implementation for Ad Networks Database

chrome/browser/extensions/activity_log/ad_network_database.h

Index: chrome/browser/extensions/activity_log/ad_network_database.h
diff --git a/chrome/browser/extensions/activity_log/ad_network_database.h b/chrome/browser/extensions/activity_log/ad_network_database.h
index a2e349bb521cc6c7a538b5a2fbb0a063352d6c49..483f2b3d2dcbdefac97011616e21e38a3540ce06 100644
--- a/chrome/browser/extensions/activity_log/ad_network_database.h
+++ b/chrome/browser/extensions/activity_log/ad_network_database.h
@@ -20,6 +20,11 @@ class AdNetworkDatabase {
   static const AdNetworkDatabase* Get();
   static void SetForTesting(scoped_ptr<AdNetworkDatabase> database);
 
+  // Returns true if the database is enabled (is ready to properly detect
+  // ad networks).
+  virtual bool IsEnabled() const = 0;
+
+  // Returns true if the url is in the list of known ad networks.
   virtual bool IsAdNetwork(const GURL& url) const = 0;
 };