Change userid from a uint32_t to a string guid

mash/quick_launch/quick_launch_application.h

Index: mash/quick_launch/quick_launch_application.h
diff --git a/mash/quick_launch/quick_launch_application.h b/mash/quick_launch/quick_launch_application.h
index c95f2a2c54c6119200ebae328bde2f929cbfa399..8fbd65089d904f3d14895d96df3beb2036288152 100644
--- a/mash/quick_launch/quick_launch_application.h
+++ b/mash/quick_launch/quick_launch_application.h
@@ -26,8 +26,8 @@ class QuickLaunchApplication : public mojo::ShellClient {
   // mojo::ShellClient:
   void Initialize(mojo::Connector* connector,
                   const std::string& url,
-                  uint32_t id,
-                  uint32_t user_id) override;
+                  const std::string& user_id,
+                  uint32_t id) override;
   bool AcceptConnection(mojo::Connection* connection) override;
 
   mojo::TracingImpl tracing_;