Revert of chromeos: Makes mushrome use simplified display management

services/ui/ws/window_server.cc

Index: services/ui/ws/window_server.cc
diff --git a/services/ui/ws/window_server.cc b/services/ui/ws/window_server.cc
index c1fff169fc9dcddf0c9b6f3360b2167665bafbb2..f48149ee5dd483917c1e429a9702f8da3553e522 100644
--- a/services/ui/ws/window_server.cc
+++ b/services/ui/ws/window_server.cc
@@ -31,33 +31,6 @@
 namespace ui {
 namespace ws {
 
-namespace {
-
-// Returns true if |window| is considered the active window manager for
-// |display|.
-bool IsWindowConsideredWindowManagerRoot(const Display* display,
-                                         const ServerWindow* window) {
-  if (!display)
-    return false;
-
-  const WindowManagerDisplayRoot* display_root =
-      display->GetActiveWindowManagerDisplayRoot();
-  if (!display_root)
-    return false;
-
-  if (window == display_root->root())
-    return true;
-
-  // If the window manager manually creates displays then there is an extra
-  // window, the window supplied via SetDisplayRoot().
-  return !display_root->window_manager_state()
-              ->window_tree()
-              ->automatically_create_display_roots() &&
-         window->parent() == display_root->root();
-}
-
-}  // namespace
-
 struct WindowServer::CurrentMoveLoopState {
   uint32_t change_id;
   ServerWindow* window;
@@ -851,8 +824,8 @@
   if (!window_paint_callback_.is_null())
     window_paint_callback_.Run(window);
 
-  Display* display = display_manager_->GetDisplayContaining(window);
-  if (IsWindowConsideredWindowManagerRoot(display, window)) {
+  auto* display = display_manager_->GetDisplayContaining(window);
+  if (display && window == display->GetActiveRootWindow()) {
     // A new surface for a WindowManager root has been created. This is a
     // special case because ServerWindows created by the WindowServer are not
     // part of a WindowTree. Send the SurfaceId directly to FrameGenerator and