WIP: Propagate SurfaceID up window tree hierarchy

services/ui/ws/server_window.cc

Index: services/ui/ws/server_window.cc
diff --git a/services/ui/ws/server_window.cc b/services/ui/ws/server_window.cc
index 5a6ca3c004b0c13ffdd26a697312e39345b8acab..854b1c78d3826d0be89b04bda99e90e5f8a30366 100644
--- a/services/ui/ws/server_window.cc
+++ b/services/ui/ws/server_window.cc
@@ -338,6 +338,13 @@ std::string ServerWindow::GetName() const {
   return std::string(it->second.begin(), it->second.end());
 }
 
+bool ServerWindow::IsContainer() const {
+  auto it = properties_.find(mojom::WindowManager::kContainer_Property);
+  if (it == properties_.end())
+    return false;
+  return true;
+}
+
 void ServerWindow::SetTextInputState(const ui::TextInputState& state) {
   const bool changed = !(text_input_state_ == state);
   if (changed) {