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..b2699090f8999067d85b2c868cd016d8dde3daa8 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.
+    if (!search_model_->top_bars_visible())
+      HideAllInfoBars();
   }
 
   // Now that everything is up to date, signal the delegate to re-layout.
@@ -174,29 +179,17 @@ 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 {
+void InfoBarContainer::ModelChanged(const chrome::search::Mode& old_mode,
+                                    const chrome::search::Mode& new_mode,
+                                    bool top_bars_visible) {
+  if (!chrome::search::ShouldHandleTopBarsVisibilityChange(old_mode,
+                                                           new_mode)) {
+    return;
+  }
+  if (top_bars_visible && !infobars_shown_) {
     ChangeInfoBarService(infobar_service_);
     infobars_shown_time_ = base::TimeTicks::Now();
-  }
-}
-
-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()) {
+  } else if (!top_bars_visible && infobars_shown_) {
     HideAllInfoBars();
     OnInfoBarStateChanged(false);
   }