Rip out browser-side RID caching for most visited items.

chrome/browser/ui/search/search_tab_helper.h

Index: chrome/browser/ui/search/search_tab_helper.h
diff --git a/chrome/browser/ui/search/search_tab_helper.h b/chrome/browser/ui/search/search_tab_helper.h
index 7b0ff13c929168030b4268cbd594dca5c77696ae..8dd771100bd814bded3345f691479189a6b21cb2 100644
--- a/chrome/browser/ui/search/search_tab_helper.h
+++ b/chrome/browser/ui/search/search_tab_helper.h
@@ -5,9 +5,12 @@
 #ifndef CHROME_BROWSER_UI_SEARCH_SEARCH_TAB_HELPER_H_
 #define CHROME_BROWSER_UI_SEARCH_SEARCH_TAB_HELPER_H_
 
+#include <vector>
+
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "chrome/browser/ui/search/search_model.h"
+#include "chrome/common/instant_types.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/web_contents_observer.h"
@@ -42,6 +45,11 @@ class SearchTabHelper : public content::NotificationObserver,
   // the notification system and shouldn't call this method.
   void NavigationEntryUpdated();
 
+  // Updates |last_known_most_visited_items_| with |items|.
+  // Returns false if |items| matches the |last_known_most_visited_items_|.
+  bool UpdateLastKnownMostVisitedItems(
+      const std::vector<InstantMostVisitedItem>& items);
+
  private:
   friend class content::WebContentsUserData<SearchTabHelper>;
 
@@ -77,6 +85,10 @@ class SearchTabHelper : public content::NotificationObserver,
 
   content::WebContents* web_contents_;
 
+  // Tracks the last set of most visited items sent to the InstantPage renderer.
+  // Used to prevent sending duplicate IPC messages to the renderer.
+  std::vector<InstantMostVisitedItem> last_known_most_visited_items_;
+
   DISALLOW_COPY_AND_ASSIGN(SearchTabHelper);
 };