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

chrome/browser/ui/search/search_model.h

Index: chrome/browser/ui/search/search_model.h
diff --git a/chrome/browser/ui/search/search_model.h b/chrome/browser/ui/search/search_model.h
index 6a7f1f138742d451a740290f5e5cc7a4c82b295a..01ec5cbf16db858d8bbe55ee05252e40e404cec1 100644
--- a/chrome/browser/ui/search/search_model.h
+++ b/chrome/browser/ui/search/search_model.h
@@ -21,13 +21,19 @@ class SearchModel {
   SearchModel();
   ~SearchModel();
 
-  // Change the mode.  Change notifications are sent to observers.  An animated
-  // transition may be requested.
+  // Change the mode.  Change notifications are sent to observers.
   void SetMode(const Mode& mode);
 
+  // Set visibility of top bars (bookmark and info bars).  Notifications are
+  // sent to observers.
+  void SetTopBarsVisible(bool visible);

[dhollowa, 2013/03/08 00:03:32]

Please group this with show_top_bars().  Concepts group tighter than
getter/setter groups.

[kuan, 2013/03/12 18:00:38]

Done.

+
   // Get the active mode.
   const Mode& mode() const { return mode_; }
 
+  // Get the visibility of top bars (bookmark and info bars).
+  bool show_top_bars() const { return show_top_bars_; }
+
   // Add and remove observers.
   void AddObserver(SearchModelObserver* observer);
   void RemoveObserver(SearchModelObserver* observer);
@@ -36,6 +42,9 @@ class SearchModel {
   // The display mode of UI elements such as the toolbar, the tab strip, etc.
   Mode mode_;
 
+  // The visibility of top bars (bookmark and info bars).
+  bool show_top_bars_;
+
   // Observers.
   ObserverList<SearchModelObserver> observers_;