More user id tracking for mus:

components/mus/ws/window_manager_factory_service.h

Index: components/mus/ws/window_manager_factory_service.h
diff --git a/components/mus/ws/window_manager_factory_service.h b/components/mus/ws/window_manager_factory_service.h
index 94ffa3c0bd44ee245691703694d71dfc506c9c46..103217477bdfb6446e4a8f401a7eb9fa1eddfd70 100644
--- a/components/mus/ws/window_manager_factory_service.h
+++ b/components/mus/ws/window_manager_factory_service.h
@@ -8,6 +8,7 @@
 #include <stdint.h>
 
 #include "components/mus/public/interfaces/window_manager_factory.mojom.h"
+#include "components/mus/ws/user_id.h"
 #include "mojo/public/cpp/bindings/binding.h"
 
 namespace mus {
@@ -16,30 +17,44 @@ namespace ws {
 class ServerWindow;
 class WindowManagerFactoryRegistry;
 
+namespace test {
+class WindowManagerFactoryRegistryTestApi;
+}
+
 class WindowManagerFactoryService : public mojom::WindowManagerFactoryService {
  public:
   WindowManagerFactoryService(
       WindowManagerFactoryRegistry* registry,
-      uint32_t user_id,
+      UserId user_id,
       mojo::InterfaceRequest<mojom::WindowManagerFactoryService> request);
   ~WindowManagerFactoryService() override;
 
-  uint32_t user_id() const { return user_id_; }
+  UserId user_id() const { return user_id_; }
 
   mojom::WindowManagerFactory* window_manager_factory() {
-    return window_manager_factory_.get();
+    return window_manager_factory_;
   }
 
   // mojom::WindowManagerFactoryService:
   void SetWindowManagerFactory(mojom::WindowManagerFactoryPtr factory) override;
 
  private:
+  friend class test::WindowManagerFactoryRegistryTestApi;
+
+  // Used by tests.
+  WindowManagerFactoryService(WindowManagerFactoryRegistry* registry,
+                              UserId user_id);
+
+  void SetWindowManagerFactoryImpl(mojom::WindowManagerFactory* factory);
   void OnConnectionLost();
 
   WindowManagerFactoryRegistry* registry_;
-  const uint32_t user_id_;
+  const UserId user_id_;
   mojo::Binding<mojom::WindowManagerFactoryService> binding_;
-  mojom::WindowManagerFactoryPtr window_manager_factory_;
+  mojom::WindowManagerFactoryPtr window_manager_factory_ptr_;
+  // Typically the same as |window_manager_factory_ptr_|, but differs for
+  // tests that don't create bindings.
+  mojom::WindowManagerFactory* window_manager_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowManagerFactoryService);
 };