[Instant] Default Search Provider change redirects to local NTP in some cases

chrome/browser/search/instant_service_observer.h

 // 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.
 
 #ifndef CHROME_BROWSER_SEARCH_INSTANT_SERVICE_OBSERVER_H_
 #define CHROME_BROWSER_SEARCH_INSTANT_SERVICE_OBSERVER_H_
 
 #include <vector>
 
 struct InstantMostVisitedItem;
 struct ThemeBackgroundInfo;
 
 // InstantServiceObserver defines the observer interface for InstantService.
 class InstantServiceObserver {
  public:
   // Indicates that the user's custom theme has changed in some way.
   virtual void ThemeInfoChanged(const ThemeBackgroundInfo&);
 
   // Indicates that the most visited items has changed.
   virtual void MostVisitedItemsChanged(
       const std::vector<InstantMostVisitedItem>&);
 
-  // Indicates that the default search provider changed.
-  virtual void DefaultSearchProviderChanged();
+  // Indicates that the default search provider changed. Parameter indicates
+  // whether the Google base URL changed (such as when the user migrates from
+  // one google.<TLD> to another TLD).
+  virtual void DefaultSearchProviderChanged(
+      bool google_base_url_domain_changed);
 
   // Indicates that the omnibox start margin has changed.
   virtual void OmniboxStartMarginChanged(int omnibox_start_margin);
 
  protected:
   virtual ~InstantServiceObserver() {}
 };
 
 #endif  // CHROME_BROWSER_SEARCH_INSTANT_SERVICE_OBSERVER_H_