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

chrome/browser/infobars/infobar_container.h

Index: chrome/browser/infobars/infobar_container.h
diff --git a/chrome/browser/infobars/infobar_container.h b/chrome/browser/infobars/infobar_container.h
index 508bf76dd23826c5d8ecda213526b6d07069a2ea..d0f3439b0835251e49b81bd57e3d6485b95debbe 100644
--- a/chrome/browser/infobars/infobar_container.h
+++ b/chrome/browser/infobars/infobar_container.h
@@ -9,6 +9,7 @@
 
 #include "base/compiler_specific.h"
 #include "base/time.h"
+#include "chrome/browser/instant/instant_model_observer.h"
 #include "chrome/browser/ui/search/search_model_observer.h"
 #include "chrome/common/search_types.h"
 #include "content/public/browser/notification_observer.h"
@@ -18,6 +19,7 @@
 class InfoBar;
 class InfoBarDelegate;
 class InfoBarService;
+class InstantModel;
 
 namespace chrome {
 namespace search {
@@ -33,16 +35,25 @@ class SearchModel;
 // Platforms need to subclass this to implement a few platform-specific
 // functions, which are pure virtual here.
 //
-// This class also observes changes to the SearchModel mode. If the user changes
-// into suggestions mode, it hides all the infobars temporarily.  When the user
-// changes back out of suggestions mode, it reshows any infobars, and starts a
-// 50 ms window during which any attempts to re-hide any infobars are handled
-// without animation.  This prevents glitchy-looking behavior when the user
-// navigates following a mode change, which otherwise would re-show the infobars
-// only to instantly animate them closed.  The window is canceled if a tab
-// change occurs.
+// This class also observes changes to the SearchModel and InstantModel modes.
+// It hides infobars temporarily if the user changes into |SEARCH_SUGGESTIONS|
+// mode (refer to chrome::search::Mode in chrome/common/search_types.h for all
+// search modes) when:
+// - on a page that is not |NTP| or |SEARCH_RESULTS|: when instant preview is
+//   ready;
+// - on a page that is |NTP| or |SEARCH_RESULTS|: immediately;
+//   TODO(kuan): this scenario requires more complex synchronization with
+//   renderer SearchBoxAPI and will be implemented as the next step;
+//   for now, hiding is immediate.
+// When the user changes back out of |SEARCH_SUGGESTIONS| mode, it reshows any
+// infobars, and starts a 50 ms window during which any attempts to re-hide any
+// infobars are handled without animation.  This prevents glitchy-looking
+// behavior when the user navigates following a mode change, which otherwise
+// would re-show the infobars only to instantly animate them closed.  The window
+// to re-hide infobars without animation is canceled if a tab change occurs.
 class InfoBarContainer : public content::NotificationObserver,
-                         public chrome::search::SearchModelObserver  {
+                         public chrome::search::SearchModelObserver,
+                         public InstantModelObserver  {
  public:
   class Delegate {
    public:
@@ -61,10 +72,11 @@ class InfoBarContainer : public content::NotificationObserver,
     virtual ~Delegate();
   };
 
-  // |search_model| may be NULL if this class is used in a window that does not
-  // support Instant Extended.
+  // |search_model| and |instant_model| may be NULL if this class is used in a
+  // window that does not support Instant Extended.
   InfoBarContainer(Delegate* delegate,
-                   chrome::search::SearchModel* search_model);
+                   chrome::search::SearchModel* search_model,
+                   const InstantModel* instant_model);
   virtual ~InfoBarContainer();
 
   // Changes the InfoBarService for which this container is showing
@@ -126,6 +138,9 @@ class InfoBarContainer : public content::NotificationObserver,
   virtual void ModeChanged(const chrome::search::Mode& old_mode,
                            const chrome::search::Mode& new_mode) OVERRIDE;
 
+  // InstantModelObserver:
+  virtual void PreviewStateChanged(const InstantModel& model) OVERRIDE;
+
   // Hides an InfoBar for the specified delegate, in response to a notification
   // from the selected InfoBarService.  The InfoBar's disappearance will be
   // animated if |use_animation| is true and it has been more than 50ms since
@@ -165,6 +180,9 @@ class InfoBarContainer : public content::NotificationObserver,
   // Extended.
   chrome::search::SearchModel* search_model_;
 
+  // Tracks state of instant preview for Instant Extended.
+  const InstantModel* instant_model_;  // Weak.
+
   // Calculated in SetMaxTopArrowHeight().
   int top_arrow_target_height_;