Unify display ids between Display and PlatformDisplay.

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 461c9274059fb5a74442d3db6071fffdc8bc9601..fb500d96ed2be8e87e0f6c59522419159fa153dc 100644
--- a/services/ui/ws/window_tree.cc
+++ b/services/ui/ws/window_tree.cc
@@ -100,7 +100,7 @@ void WindowTree::Init(std::unique_ptr<WindowTreeBinding> binding,
 
   Display* display = GetDisplay(root);
   int64_t display_id =
-      display ? display->id() : display::Display::kInvalidDisplayID;
+      display ? display->GetId() : display::Display::kInvalidDisplayID;
   const ServerWindow* focused_window =
       display ? display->GetFocusedWindow() : nullptr;
   if (focused_window)
@@ -413,7 +413,7 @@ void WindowTree::OnWindowManagerCreatedTopLevelWindow(
   roots_.insert(window);
   Display* display = GetDisplay(window);
   int64_t display_id =
-      display ? display->id() : display::Display::kInvalidDisplayID;
+      display ? display->GetId() : display::Display::kInvalidDisplayID;
   const bool drawn = window->parent() && window->parent()->IsDrawn();
   client()->OnTopLevelCreated(client_change_id, WindowToWindowData(window),
                               display_id, drawn);