Implement Non-Closable Notification

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 95933305a0e65f78018174b933611bac208969f6..d2e95909df2e0a4a5ba073b550ce098e40f3fa9e 100644
--- a/ui/message_center/views/message_list_view.cc
+++ b/ui/message_center/views/message_list_view.cc
@@ -191,17 +191,24 @@ void MessageListView::ResetRepositionSession() {
   fixed_height_ = 0;
 }
 
-void MessageListView::ClearAllNotifications(
+void MessageListView::ClearAllClosableNotifications(

[dewittj, 2016/02/08 18:02:34]

How does the clear-all animation look when there are some non-closable
notifications visible in the message center when you hit the clear all button? 
Since you skipp the closable one, you may need some more animations to signal
that this one is not getting closed.

[yoshiki, 2016/02/09 23:42:25]

Android dosen't have any animation for non-closable notifications. So I think
it's ok. WDYT? 

[dewittj, 2016/02/10 00:03:15]

Does the ChromeOS notification center close itself if clear-all is pressed with
a pinned notification, or does it remain open?

     const gfx::Rect& visible_scroll_rect) {
   for (int i = 0; i < child_count(); ++i) {
-    views::View* child = child_at(i);
+    // Safe cast since all views in MessageListView are MessageViews.
+    MessageView* child = (MessageView*)child_at(i);
     if (!child->visible())
       continue;
     if (gfx::IntersectRects(child->bounds(), visible_scroll_rect).IsEmpty())
       continue;
+    if (!child->IsClosable())
+      continue;
     clearing_all_views_.push_back(child);
   }
-  DoUpdateIfPossible();
+  if (clearing_all_views_.empty()) {
+    message_center_view()->OnAllNotificationsCleared();
+  } else {
+    DoUpdateIfPossible();
+  }
 }
 
 void MessageListView::OnBoundsAnimatorProgressed(