Move shell service to toplevel shell namespace

services/tracing/main.cc

Index: services/tracing/main.cc
diff --git a/services/tracing/main.cc b/services/tracing/main.cc
index 9142263fcf391b004aafb29f6e34d0f6a58b3a6f..758efedf985a0df05f8ddeef5fa9cd3a9c4daaca 100644
--- a/services/tracing/main.cc
+++ b/services/tracing/main.cc
@@ -7,6 +7,6 @@
 #include "services/tracing/tracing_app.h"
 
 MojoResult MojoMain(MojoHandle shell_handle) {
-  mojo::ApplicationRunner runner(new tracing::TracingApp);
+  shell::ApplicationRunner runner(new tracing::TracingApp);
   return runner.Run(shell_handle);
 }