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

chrome/browser/infobars/infobar_container.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_INFOBARS_INFOBAR_CONTAINER_H_
 #define CHROME_BROWSER_INFOBARS_INFOBAR_CONTAINER_H_
 
 #include <vector>
 
 #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"
 #include "content/public/browser/notification_registrar.h"
 #include "third_party/skia/include/core/SkColor.h"
 
 class InfoBar;
 class InfoBarDelegate;
 class InfoBarService;
 
 namespace chrome {
 namespace search {
 class SearchModel;
 }
 }
 
 // InfoBarContainer is a cross-platform base class to handle the visibility-
 // related aspects of InfoBars.  While InfoBars own themselves, the
 // InfoBarContainer is responsible for telling particular InfoBars that they
 // should be hidden or visible.
 //
 // 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 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 :
+// - |DEFAULT| page: when instant preview is ready;
+// - |NTP| or |SEARCH_RESULTS| page: 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:
     // The separator color may vary depending on where the container is hosted.
     virtual SkColor GetInfoBarSeparatorColor() const = 0;
 
     // The delegate is notified each time the infobar container changes height,
     // as well as when it stops animating.
     virtual void InfoBarContainerStateChanged(bool is_animating) = 0;
 
@@ skipping 38 matching lines @@
   // anything necessary to respond, e.g. re-layout.
   void OnInfoBarStateChanged(bool is_animating);
 
   // Called by |infobar| to request that it be removed from the container, as it
   // is about to delete itself.  At this point, |infobar| should already be
   // hidden.
   void RemoveInfoBar(InfoBar* infobar);
 
   const Delegate* delegate() const { return delegate_; }
 
+  // InstantModelObserver:
+  virtual void PreviewStateChanged(const InstantModel& model) OVERRIDE;
+
  protected:
   // Subclasses must call this during destruction, so that we can remove
   // infobars (which will call the pure virtual functions below) while the
   // subclass portion of |this| has not yet been destroyed.
   void RemoveAllInfoBarsForDestruction();
 
   // These must be implemented on each platform to e.g. adjust the visible
   // object hierarchy.
   virtual void PlatformSpecificAddInfoBar(InfoBar* infobar,
                                           size_t position) = 0;
@@ skipping 51 matching lines @@
   // Extended.
   chrome::search::SearchModel* search_model_;
 
   // Calculated in SetMaxTopArrowHeight().
   int top_arrow_target_height_;
 
   DISALLOW_COPY_AND_ASSIGN(InfoBarContainer);
 };
 
 #endif  // CHROME_BROWSER_INFOBARS_INFOBAR_CONTAINER_H_