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

chrome/browser/ui/search/search_model_observer.h

 // Copyright (c) 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_MODEL_OBSERVER_H_
 #define CHROME_BROWSER_UI_SEARCH_SEARCH_MODEL_OBSERVER_H_
 
 namespace chrome {
 namespace search {
 
 struct Mode;

[dhollowa, 2013/03/13 17:21:55]

Can get rid of this, and you'll need to include search_model.h because of the
inner struct |SearchModel::State|.

[kuan, 2013/03/13 22:21:07]

Done.

 
 // This class defines the observer interface for the |SearchModel|.
 class SearchModelObserver {
  public:
-  // Informs the observer that the mode has changed.
-  virtual void ModeChanged(const Mode& old_mode, const Mode& new_mode) = 0;
+  // Informs the observer that the model has changed.

[dhollowa, 2013/03/13 17:21:55]

"... the model's state has changed."

[kuan, 2013/03/13 22:21:07]

Done.

+  virtual void ModelChanged(const Mode& old_mode,

[dhollowa, 2013/03/13 17:21:55]

As mentioned:
virtual void ModelChanged(const SearchModel::State& old_state, const
SearchModel::State& new_state) = 0;

[kuan, 2013/03/13 22:21:07]

Done.

+                            const Mode& new_mode,
+                            bool top_bars_visible) = 0;
 
  protected:
   virtual ~SearchModelObserver() {}
 };
 
 }  // namespace search
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_UI_SEARCH_SEARCH_MODEL_OBSERVER_H_