Change userid from a uint32_t to a string guid

ash/mus/sysui_application.cc

Index: ash/mus/sysui_application.cc
diff --git a/ash/mus/sysui_application.cc b/ash/mus/sysui_application.cc
index c55482ac964d2d80eb02b39384f6ce7d3720bc22..91549478aba89a893a37867b2e67028f724a9979 100644
--- a/ash/mus/sysui_application.cc
+++ b/ash/mus/sysui_application.cc
@@ -279,8 +279,8 @@ SysUIApplication::~SysUIApplication() {}
 
 void SysUIApplication::Initialize(mojo::Connector* connector,
                                   const std::string& url,
-                                  uint32_t id,
-                                  uint32_t user_id) {
+                                  const std::string& user_id,
+                                  uint32_t id) {
   ash_init_.reset(new AshInit());
   ash_init_->Initialize(connector);
 }