app_list: Add sync animation.

ui/app_list/app_list_model.cc

Index: ui/app_list/app_list_model.cc
diff --git a/ui/app_list/app_list_model.cc b/ui/app_list/app_list_model.cc
index a4a8193f9057e6200088a071c9a7cdf4b3e0b15c..907ceffa072ce77b51ca50fe525e02d8307c6383 100644
--- a/ui/app_list/app_list_model.cc
+++ b/ui/app_list/app_list_model.cc
@@ -5,6 +5,7 @@
 #include "ui/app_list/app_list_model.h"
 
 #include "ui/app_list/app_list_item_model.h"
+#include "ui/app_list/app_list_model_observer.h"
 #include "ui/app_list/search_box_model.h"
 #include "ui/app_list/search_result.h"
 
@@ -19,4 +20,22 @@ AppListModel::AppListModel()
 AppListModel::~AppListModel() {
 }
 
+void AppListModel::AddObserver(AppListModelObserver* observer) {
+  observers_.AddObserver(observer);
+}
+
+void AppListModel::RemoveObserver(AppListModelObserver* observer) {
+  observers_.RemoveObserver(observer);
+}
+
+void AppListModel::SetStatus(Status status) {
+  if (status_ == status)
+    return;
+
+  status_ = status;
+  FOR_EACH_OBSERVER(AppListModelObserver,
+                    observers_,
+                    OnAppListModelStatusChanged());
+}
+
 }  // namespace app_list