alternate ntp: fix website page jankiness when suggestions show and top bars are hidden

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 a25202563ee06c2918cbd4893d273a07bb040e7d..eed06ddd9708c2dfa9f27ae97dfdc4686eb28051 100644
--- a/chrome/browser/infobars/infobar_container.cc
+++ b/chrome/browser/infobars/infobar_container.cc
@@ -15,6 +15,7 @@
 #include "chrome/browser/api/infobars/infobar_delegate.h"
 #include "chrome/browser/api/infobars/infobar_service.h"
 #include "chrome/browser/infobars/infobar.h"
+#include "chrome/browser/instant/instant_model.h"
 #include "chrome/browser/ui/search/search_model.h"
 #include "chrome/common/chrome_notification_types.h"
 #include "content/public/browser/notification_details.h"
@@ -26,13 +27,17 @@ InfoBarContainer::Delegate::~Delegate() {
 
 InfoBarContainer::InfoBarContainer(
     Delegate* delegate,
-    chrome::search::SearchModel* search_model)
+    chrome::search::SearchModel* search_model,
+    const InstantModel* instant_model)
     : delegate_(delegate),
       infobar_service_(NULL),
       search_model_(search_model),
+      instant_model_(instant_model),
       top_arrow_target_height_(InfoBar::kDefaultArrowTargetHeight) {
   if (search_model_)
     search_model_->AddObserver(this);
+  if (instant_model_)
+    instant_model_->AddObserver(this);
 }
 
 InfoBarContainer::~InfoBarContainer() {
@@ -40,6 +45,8 @@ InfoBarContainer::~InfoBarContainer() {
   DCHECK(infobars_.empty());
   if (search_model_)
     search_model_->RemoveObserver(this);
+  if (instant_model_)
+    instant_model_->RemoveObserver(this);
 }
 
 void InfoBarContainer::ChangeInfoBarService(InfoBarService* infobar_service) {
@@ -164,6 +171,12 @@ 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 preview is ready is received via
+    // PreviewStateChanged(); this prevents jankiness caused by infobars hiding
+    // followed by suggestions appearing.
+    if (new_mode.is_origin_default())
+      return;
     HideAllInfoBars();
     OnInfoBarStateChanged(false);
   } else {
@@ -172,6 +185,16 @@ void InfoBarContainer::ModeChanged(const chrome::search::Mode& old_mode,
   }
 }
 
+void InfoBarContainer::PreviewStateChanged(const InstantModel& 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()) {
+    HideAllInfoBars();
+    OnInfoBarStateChanged(false);
+  }
+}
+
 size_t InfoBarContainer::HideInfoBar(InfoBarDelegate* delegate,
                                      bool use_animation) {
   bool should_animate = use_animation &&