[Fuchsia] implement Show, Hide and Close in ScenicWindow

Change-Id: Ia1f21d38b2e3eb04377cba774d19172718f82e91
Reviewed-on: https://chromium-review.googlesource.com/c/1344878Reviewed-by: Michael Spang <spang@chromium.org>
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609843}

ui/ozone/platform/scenic/scenic_window.cc

@@ -46,7 +46,6 @@ ScenicWindow::ScenicWindow(ScenicWindowManager* window_manager,
   parent_node_.BindAsRequest(&parent_export_token);
 
   // Setup entity node for the window.
-  parent_node_.AddChild(node_);
   node_.AddChild(shape_node_);
   shape_node_.SetMaterial(material_);
 
@@ -106,15 +105,16 @@ void ScenicWindow::SetTitle(const base::string16& title) {
 }
 
 void ScenicWindow::Show() {
-  NOTIMPLEMENTED();
+  parent_node_.AddChild(node_);
 }
 
 void ScenicWindow::Hide() {
-  NOTIMPLEMENTED();
+  node_.Detach();
 }
 
 void ScenicWindow::Close() {
-  NOTIMPLEMENTED();
+  Hide();
+  delegate_->OnClosed();
 }
 
 void ScenicWindow::PrepareForShutdown() {