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

chrome/browser/ui/search/search_delegate.cc

Index: chrome/browser/ui/search/search_delegate.cc
diff --git a/chrome/browser/ui/search/search_delegate.cc b/chrome/browser/ui/search/search_delegate.cc
index 6e437c0032f8198e338a1131ee45578cbe928355..be21773518530f5d54771d451b069c892c37f93d 100644
--- a/chrome/browser/ui/search/search_delegate.cc
+++ b/chrome/browser/ui/search/search_delegate.cc
@@ -20,8 +20,10 @@ SearchDelegate::~SearchDelegate() {
   DCHECK(!tab_model_) << "All tabs should have been deactivated or closed.";
 }
 
-void SearchDelegate::ModeChanged(const Mode& old_mode, const Mode& new_mode) {
+void SearchDelegate::ModelChanged(const Mode& old_mode, const Mode& new_mode,
+                                  bool top_bars_visible) {
   browser_model_->SetMode(new_mode);
+  browser_model_->SetTopBarsVisible(top_bars_visible);

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

This is a potential problem (having two model-changes) because it will trigger
two observer notifications.  Better to add a new SearchModel::SetState(const
SearchModel::State& state) method that transfers all state in one go.

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

Done.

 }
 
 void SearchDelegate::OnTabActivated(content::WebContents* web_contents) {
@@ -30,6 +32,7 @@ void SearchDelegate::OnTabActivated(content::WebContents* web_contents) {
   tab_model_ =
       chrome::search::SearchTabHelper::FromWebContents(web_contents)->model();
   browser_model_->SetMode(tab_model_->mode());
+  browser_model_->SetTopBarsVisible(tab_model_->top_bars_visible());

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

Ditto.

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

Done.

   tab_model_->AddObserver(this);
 }