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

chrome/browser/ui/browser.h

Index: chrome/browser/ui/browser.h
diff --git a/chrome/browser/ui/browser.h b/chrome/browser/ui/browser.h
index 35db7f34ace6430ab7f7f8e0617cb5b7e4fd3d10..6ebd2c2a6dbf96c6aae038a7608e403b6977d6eb 100644
--- a/chrome/browser/ui/browser.h
+++ b/chrome/browser/ui/browser.h
@@ -453,12 +453,6 @@ class Browser : public TabStripModelObserver,
   // Show the first run search engine bubble on the location bar.
   void ShowFirstRunBubble();
 
-  // If necessary, update the bookmark bar state according to the Instant
-  // overlay state: when Instant overlay shows suggestions and bookmark bar is
-  // still showing attached, hide it.
-  void MaybeUpdateBookmarkBarStateForInstantOverlay(
-      const chrome::search::Mode& mode);
-
   // Show a download on the download shelf.
   void ShowDownload(content::DownloadItem* download);
 
@@ -680,8 +674,9 @@ class Browser : public TabStripModelObserver,
                        const content::NotificationDetails& details) OVERRIDE;
 
   // Overridden from chrome::search::SearchModelObserver:
-  virtual void ModeChanged(const chrome::search::Mode& old_mode,
-                           const chrome::search::Mode& new_mode) OVERRIDE;
+  virtual void ModelChanged(const chrome::search::Mode& old_mode,
+                            const chrome::search::Mode& new_mode,
+                            bool top_bars_visible) OVERRIDE;
 
   // Command and state updating ///////////////////////////////////////////////