Change userid from a uint32_t to a string guid

components/mus/mus_app.cc

Index: components/mus/mus_app.cc
diff --git a/components/mus/mus_app.cc b/components/mus/mus_app.cc
index 1b42c95a8ea3de84f67018722ac67c6a45301643..f9ec70ad5ae5ccc713a68914b7ee7c662eae3a0d 100644
--- a/components/mus/mus_app.cc
+++ b/components/mus/mus_app.cc
@@ -95,8 +95,8 @@ void MandolineUIServicesApp::InitializeResources(mojo::Connector* connector) {
 
 void MandolineUIServicesApp::Initialize(mojo::Connector* connector,
                                         const std::string& url,
-                                        uint32_t id,
-                                        uint32_t user_id) {
+                                        const std::string& user_id,
+                                        uint32_t id) {
   connector_ = connector;
   surfaces_state_ = new SurfacesState;