Change userid from a uint32_t to a string guid

mash/task_viewer/task_viewer.h

Index: mash/task_viewer/task_viewer.h
diff --git a/mash/task_viewer/task_viewer.h b/mash/task_viewer/task_viewer.h
index 5de60288416d85e5a5f4573d17202578dee56d16..0a696cdb07ef92d56c3a7c72fade1124a134cd0c 100644
--- a/mash/task_viewer/task_viewer.h
+++ b/mash/task_viewer/task_viewer.h
@@ -28,7 +28,7 @@ class TaskViewer : public mojo::ShellClient {
  private:
   // 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;
 
   mojo::TracingImpl tracing_;
   scoped_ptr<views::AuraInit> aura_init_;