Add a user id parameter to connections

mojo/shell/public/cpp/shell.h

Index: mojo/shell/public/cpp/shell.h
diff --git a/mojo/shell/public/cpp/shell.h b/mojo/shell/public/cpp/shell.h
index 3b12cc932e3fb0063dfea8337cf3113f2be79f8f..f513f40d35a0f9425bd99833acec95311488e0ca 100644
--- a/mojo/shell/public/cpp/shell.h
+++ b/mojo/shell/public/cpp/shell.h
@@ -47,10 +47,13 @@ class Shell {
     void set_filter(shell::mojom::CapabilityFilterPtr filter) {
       filter_ = std::move(filter);
     }
+    void set_user_id(uint32_t user_id) { user_id_ = user_id; }
+    uint32_t user_id() const { return user_id_; }
 
    private:
     GURL url_;
     shell::mojom::CapabilityFilterPtr filter_;
+    uint32_t user_id_;
 
     DISALLOW_COPY_AND_ASSIGN(ConnectParams);
   };