alternate ntp: implement Show/HideBars API to reduce jank when showing/hiding bars

chrome/browser/ui/search/search_tab_helper.h

 // Copyright 2012 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_UI_SEARCH_SEARCH_TAB_HELPER_H_
 #define CHROME_BROWSER_UI_SEARCH_SEARCH_TAB_HELPER_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "chrome/browser/ui/search/search_model.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
+#include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
 
 namespace content {
 class WebContents;
 }
 
 namespace chrome {
 namespace search {
 
 // Per-tab search "helper".  Acts as the owner and controller of the tab's
 // search UI model.
 class SearchTabHelper : public content::NotificationObserver,
+                        public content::WebContentsObserver,
                         public content::WebContentsUserData<SearchTabHelper> {
  public:
   virtual ~SearchTabHelper();
 
   SearchModel* model() {
     return &model_;
   }
 
   // Invoked when the OmniboxEditModel changes state in some way that might
   // affect the search mode.
   void OmniboxEditModelChanged(bool user_input_in_progress, bool cancelling);
 
   // Invoked when the active navigation entry is updated in some way that might
   // affect the search mode. This is used by Instant when it "fixes up" the
   // virtual URL of the active entry. Regular navigations are captured through
   // the notification system and shouldn't call this method.
   void NavigationEntryUpdated();
 
  private:
   friend class content::WebContentsUserData<SearchTabHelper>;
 
   explicit SearchTabHelper(content::WebContents* web_contents);
 
   // Overridden from content::NotificationObserver:
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // Overridden from contents::WebContentsObserver:
+  virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
+
   // Sets the mode of the model based on the current URL of web_contents().
   void UpdateModel();
 
+  // Handlers for SearchBox API to show and hide top bars (bookmark and info
+  // bars).
+  void OnSearchBoxShowBars(int page_id);
+  void OnSearchBoxHideBars(int page_id);
+
   const bool is_search_enabled_;
 
   // Tracks the last value passed to OmniboxEditModelChanged().
   bool user_input_in_progress_;
 
   // Model object for UI that cares about search state.
   SearchModel model_;
 
   content::NotificationRegistrar registrar_;
 
   content::WebContents* web_contents_;
 
   DISALLOW_COPY_AND_ASSIGN(SearchTabHelper);
 };
 
 }  // namespace search
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_UI_SEARCH_SEARCH_TAB_HELPER_H_