Don't shrink the message center height while open

ui/message_center/views/message_center_view.cc

Index: ui/message_center/views/message_center_view.cc
diff --git a/ui/message_center/views/message_center_view.cc b/ui/message_center/views/message_center_view.cc
index 375d42be82d5bd5532a66982c25208c3d9056774..0bc9d1011d430b4e1958bb0af1a8227e1170735a 100644
--- a/ui/message_center/views/message_center_view.cc
+++ b/ui/message_center/views/message_center_view.cc
@@ -22,6 +22,7 @@
 #include "ui/message_center/message_center_style.h"
 #include "ui/message_center/message_center_tray.h"
 #include "ui/message_center/message_center_types.h"
+#include "ui/message_center/views/custom_notification_view.h"
 #include "ui/message_center/views/message_center_button_bar.h"
 #include "ui/message_center/views/message_list_view.h"
 #include "ui/message_center/views/message_view.h"
@@ -105,6 +106,7 @@ MessageCenterView::MessageCenterView(MessageCenter* message_center,
   scroller_->layer()->SetMasksToBounds(true);
 
   message_list_view_.reset(new MessageListView());
+  message_list_view_->set_scroller(scroller_);
   message_list_view_->set_owned_by_client();
   message_list_view_->AddObserver(this);
 
@@ -395,6 +397,7 @@ bool MessageCenterView::SetRepositionTarget() {
   if (message_list_view_->IsMouseHovered()) {
     for (const auto& hover_id_view : notification_views_) {
       MessageView* hover_view = hover_id_view.second;
+
       if (hover_view->IsMouseHovered()) {
         message_list_view_->SetRepositionTarget(hover_view->bounds());
         return true;