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

chrome/browser/infobars/infobar_container.cc

Index: chrome/browser/infobars/infobar_container.cc
diff --git a/chrome/browser/infobars/infobar_container.cc b/chrome/browser/infobars/infobar_container.cc
index b601744e09fac3f45aca280186dab6b1d419ac9d..b0fa3d41f844d4709c3e179dcdbcca695e32efbf 100644
--- a/chrome/browser/infobars/infobar_container.cc
+++ b/chrome/browser/infobars/infobar_container.cc
@@ -16,6 +16,7 @@
 #include "chrome/browser/api/infobars/infobar_service.h"
 #include "chrome/browser/infobars/infobar.h"
 #include "chrome/browser/instant/instant_overlay_model.h"
+#include "chrome/browser/instant/search.h"
 #include "chrome/browser/ui/search/search_model.h"
 #include "chrome/common/chrome_notification_types.h"
 #include "content/public/browser/notification_details.h"
@@ -73,6 +74,10 @@ void InfoBarContainer::ChangeInfoBarService(InfoBarService* infobar_service) {
               infobar_service_),
           i, false, NO_CALLBACK);
     }
+
+    // Hide infobars if search model requires so.

[Peter Kasting, 2013/03/15 05:32:01]

Don't do this.

Instead, make this function begin as follows:

  infobar_service_ = infobar_service;

  if (!search_model_->top_bars_visible())
    return;

  ...everything from the existing function except the opening RemoveAll() call
and the already-done setting of infobar_service_...

Then add "registrar_.RemoveAll();" to the top of HideAllInfoBars(), and change
the beginning of Observe() to:

  // When infobars are hidden, we shouldn't be listening for notifications.
  DCHECK(infobars_shown_);

[kuan, 2013/03/15 15:53:49]

Done.

[kuan, 2013/03/15 16:32:17]

i moved HideAllInfoBars() to start of function.  correct me if i'm wrong, but i
think we need to do this whenever tab is detached or changed, which is when this
function is called  from outside like BrowserView?

+    if (!search_model_->top_bars_visible())
+      HideAllInfoBars();
   }
 
   // Now that everything is up to date, signal the delegate to re-layout.
@@ -174,29 +179,18 @@ void InfoBarContainer::Observe(int type,
   }
 }
 
-void InfoBarContainer::ModeChanged(const chrome::search::Mode& old_mode,
-                                   const chrome::search::Mode& new_mode) {
-  // Hide infobars when showing Instant Extended suggestions.
-  if (new_mode.is_search_suggestions()) {
-    // If suggestions are being shown on a |DEFAULT| page, delay the hiding
-    // until notification that Instant overlay is ready is received via
-    // OverlayStateChanged(); this prevents jankiness caused by infobars hiding
-    // followed by suggestions appearing.
-    if (new_mode.is_origin_default())
-      return;
-    HideAllInfoBars();
-    OnInfoBarStateChanged(false);
-  } else {
-    ChangeInfoBarService(infobar_service_);
-    infobars_shown_time_ = base::TimeTicks::Now();
+void InfoBarContainer::ModelChanged(
+    const chrome::search::SearchModel::State& old_state,
+    const chrome::search::SearchModel::State& new_state) {
+  if (!chrome::search::SearchModel::ShouldChangeTopBarsVisibility(old_state,
+                                                                  new_state)) {

[Peter Kasting, 2013/03/15 05:32:01]

Nit: No {}

[kuan, 2013/03/15 15:53:49]

Done.

+    return;
   }
-}
 
-void InfoBarContainer::OverlayStateChanged(const InstantOverlayModel& model) {
-  // If suggestions are being shown on a |DEFAULT| page, hide the infobars now.
-  // See comments for ModeChanged() for explanation.
-  if (model.mode().is_search_suggestions() &&
-      model.mode().is_origin_default()) {
+  if (new_state.top_bars_visible && !infobars_shown_) {
+    ChangeInfoBarService(infobar_service_);
+    infobars_shown_time_ = base::TimeTicks::Now();
+  } else if (!new_state.top_bars_visible && infobars_shown_) {
     HideAllInfoBars();
     OnInfoBarStateChanged(false);
   }