SuggestionsService: implement SyncServiceObserver

chrome/browser/android/most_visited_sites.h

Index: chrome/browser/android/most_visited_sites.h
diff --git a/chrome/browser/android/most_visited_sites.h b/chrome/browser/android/most_visited_sites.h
index 33fdca54eeb2d1351652a93f709cf571f9a64efe..6324efd9760baa055e62cab6f383f33e90eb65ff 100644
--- a/chrome/browser/android/most_visited_sites.h
+++ b/chrome/browser/android/most_visited_sites.h
@@ -22,7 +22,7 @@
 #include "components/history/core/browser/history_types.h"
 #include "components/history/core/browser/top_sites_observer.h"
 #include "components/suggestions/proto/suggestions.pb.h"
-#include "components/sync_driver/sync_service_observer.h"
+#include "components/suggestions/suggestions_service.h"
 #include "url/gurl.h"
 
 namespace suggestions {
@@ -37,8 +37,7 @@ class PopularSites;
 class Profile;
 
 // Provides the list of most visited sites and their thumbnails to Java.
-class MostVisitedSites : public sync_driver::SyncServiceObserver,
-                         public history::TopSitesObserver,
+class MostVisitedSites : public history::TopSitesObserver,
                          public SupervisedUserServiceObserver {
  public:
   explicit MostVisitedSites(Profile* profile);
@@ -68,9 +67,6 @@ class MostVisitedSites : public sync_driver::SyncServiceObserver,
       jint index,
       jint tile_type);
 
-  // sync_driver::SyncServiceObserver implementation.
-  void OnStateChanged() override;
-
   // SupervisedUserServiceObserver implementation.
   void OnURLFilterChanged() override;
 
@@ -178,7 +174,8 @@ class MostVisitedSites : public sync_driver::SyncServiceObserver,
       SuggestionsVector* src_suggestions,
       SuggestionsVector* dst_suggestions);
 
-  // Notify the Java side observer about the availability of Most Visited Urls.
+  // Notifies the Java side observer about the availability of suggestions.
+  // Also records impressions UMA if not done already.
   void NotifyMostVisitedURLsObserver();
 
   void OnPopularSitesAvailable(bool success);
@@ -229,6 +226,10 @@ class MostVisitedSites : public sync_driver::SyncServiceObserver,
   // recorded once both the previous flags are true.
   bool recorded_uma_;
 
+  scoped_ptr<
+      suggestions::SuggestionsService::ResponseCallbackList::Subscription>
+      suggestions_subscription_;
+
   ScopedObserver<history::TopSites, history::TopSitesObserver> scoped_observer_;
 
   MostVisitedSource mv_source_;