Change userid from a uint32_t to a string guid

mash/quick_launch/quick_launch_application.cc

Index: mash/quick_launch/quick_launch_application.cc
diff --git a/mash/quick_launch/quick_launch_application.cc b/mash/quick_launch/quick_launch_application.cc
index d378d9edf1f51789fed18e7a4e2165fbb2be3241..d00baf3ee7b59f900849a030d1c9562977e0d5bf 100644
--- a/mash/quick_launch/quick_launch_application.cc
+++ b/mash/quick_launch/quick_launch_application.cc
@@ -90,8 +90,8 @@ QuickLaunchApplication::~QuickLaunchApplication() {}
 
 void QuickLaunchApplication::Initialize(mojo::Connector* connector,
                                         const std::string& url,
-                                        uint32_t id,
-                                        uint32_t user_id) {
+                                        const std::string& user_id,
+                                        uint32_t id) {
   tracing_.Initialize(connector, url);
 
   aura_init_.reset(new views::AuraInit(connector, "views_mus_resources.pak"));