Add unittest for MessageListView

ui/message_center/views/message_list_view.cc

Index: ui/message_center/views/message_list_view.cc
diff --git a/ui/message_center/views/message_list_view.cc b/ui/message_center/views/message_list_view.cc
index a5f2a70a2fd939df21fed5c11775b6cd8ecf811f..2522d458f0b4aaac13cc9e4a2c5ae03016772301 100644
--- a/ui/message_center/views/message_list_view.cc
+++ b/ui/message_center/views/message_list_view.cc
@@ -23,10 +23,8 @@ namespace {
 const int kAnimateClearingNextNotificationDelayMS = 40;
 }  // namespace
 
-MessageListView::MessageListView(MessageCenterView* message_center_view,
-                                 bool top_down)
-    : message_center_view_(message_center_view),
-      reposition_top_(-1),
+MessageListView::MessageListView(bool top_down)
+    : reposition_top_(-1),
       fixed_height_(0),
       has_deferred_task_(false),
       clear_all_started_(false),
@@ -209,12 +207,21 @@ void MessageListView::ClearAllClosableNotifications(
     clearing_all_views_.push_back(child);
   }
   if (clearing_all_views_.empty()) {
-    message_center_view()->OnAllNotificationsCleared();
+    for (auto& observer : observers_)
+      observer.OnAllNotificationsCleared();
   } else {
     DoUpdateIfPossible();
   }
 }
 
+void MessageListView::AddObserver(MessageListView::Observer* observer) {
+  observers_.AddObserver(observer);
+}
+
+void MessageListView::RemoveObserver(MessageListView::Observer* observer) {
+  observers_.RemoveObserver(observer);
+}
+
 void MessageListView::OnBoundsAnimatorProgressed(
     views::BoundsAnimator* animator) {
   DCHECK_EQ(&animator_, animator);
@@ -232,7 +239,8 @@ void MessageListView::OnBoundsAnimatorDone(views::BoundsAnimator* animator) {
 
   if (clear_all_started_) {
     clear_all_started_ = false;
-    message_center_view()->OnAllNotificationsCleared();
+    for (auto& observer : observers_)
+      observer.OnAllNotificationsCleared();
   }
 
   if (has_deferred_task_) {