Don't shrink the message center height while open

ui/message_center/views/message_center_view.cc

 // Copyright (c) 2013 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.
 
 #include "ui/message_center/views/message_center_view.h"
 
 #include <list>
 #include <map>
 
 #include "base/macros.h"
@@ skipping 87 matching lines @@
   scroller_->SetVerticalScrollBar(new views::OverlayScrollBar(false));
   scroller_->SetHorizontalScrollBar(new views::OverlayScrollBar(true));
   scroller_->set_background(
       views::Background::CreateSolidBackground(kMessageCenterBackgroundColor));
 
   scroller_->SetPaintToLayer();
   scroller_->layer()->SetFillsBoundsOpaquely(false);
   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);
 
   // We want to swap the contents of the scroll view between the empty list
   // view and the message list view, without constructing them afresh each
   // time.  So, since the scroll view deletes old contents each time you
   // set the contents (regardless of the |owned_by_client_| setting) we need
   // an intermediate view for the contents whose children we can swap in and
   // out.
   views::View* scroller_contents = new views::View();
@@ skipping 270 matching lines @@
   Update(true /* animate */);
 }
 
 // This is a separate function so we can override it in tests.
 bool MessageCenterView::SetRepositionTarget() {
   // Set the item on the mouse cursor as the reposition target so that it
   // should stick to the current position over the update.
   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;
       }
     }
   }
   return false;
 }
 
 void MessageCenterView::OnNotificationUpdated(const std::string& id) {
@@ skipping 257 matching lines @@
     // Disable the close-all button since no notification is visible.
     button_bar_->SetCloseAllButtonEnabled(false);
   }
 }
 
 void MessageCenterView::SetNotificationViewForTest(MessageView* view) {
   message_list_view_->AddNotificationAt(view, 0);
 }
 
 }  // namespace message_center