ui: Cleanup class/struct forward declarations

services/ui/ws/window_tree.cc

Index: services/ui/ws/window_tree.cc
diff --git a/services/ui/ws/window_tree.cc b/services/ui/ws/window_tree.cc
index f51b6ecbf80318f7f24e4524da7ad98e2e604b80..e4ad6630a5854f92e9733b038600869c49ff494d 100644
--- a/services/ui/ws/window_tree.cc
+++ b/services/ui/ws/window_tree.cc
@@ -585,10 +585,6 @@ void WindowTree::ProcessWindowHierarchyChanged(const ServerWindow* window,
                                                const ServerWindow* old_parent,
                                                bool originated_change) {
   const bool knows_new = new_parent && IsWindowKnown(new_parent);
-  if (originated_change && !IsWindowKnown(window) && knows_new) {
-    std::vector<const ServerWindow*> unused;
-    GetUnknownWindowsFrom(window, &unused);
-  }
   if (originated_change || (window_server_->current_operation_type() ==
                             OperationType::DELETE_WINDOW) ||
       (window_server_->current_operation_type() == OperationType::EMBED) ||
@@ -899,9 +895,16 @@ bool WindowTree::DeleteWindowImpl(WindowTree* source, ServerWindow* window) {
 void WindowTree::GetUnknownWindowsFrom(
     const ServerWindow* window,
     std::vector<const ServerWindow*>* windows) {
-  if (IsWindowKnown(window) || !access_policy_->CanGetWindowTree(window))
+  if (!access_policy_->CanGetWindowTree(window))
     return;
+
+  // This function is called in the context of a hierarchy change when the
+  // parent wasn't known. We need to tell the client about the window so that
+  // it can set the parent correctly.
   windows->push_back(window);
+  if (IsWindowKnown(window))
+    return;
+
   // There are two cases where this gets hit:
   // . During init, in which case using the window id as the client id is
   //   fine.