Revert of Quit the message loop by default in ShellConnectionLost when ApplicationRunner is used

mojo/services/tracing/tracing_app.cc

Index: mojo/services/tracing/tracing_app.cc
diff --git a/mojo/services/tracing/tracing_app.cc b/mojo/services/tracing/tracing_app.cc
index d921a6d97b9d00038f049795a527f16b3a0c45fc..65b44219b2540cfda0d94528acf450701136f6c6 100644
--- a/mojo/services/tracing/tracing_app.cc
+++ b/mojo/services/tracing/tracing_app.cc
@@ -42,12 +42,8 @@
   return true;
 }
 
-bool TracingApp::ShellConnectionLost() {
-  // TODO(beng): This is only required because TracingApp isn't run by
-  // ApplicationRunner - instead it's launched automatically by the standalone
-  // shell. It shouldn't be.
+void TracingApp::ShellConnectionLost() {
   base::MessageLoop::current()->QuitWhenIdle();
-  return false;
 }
 
 void TracingApp::Create(mojo::Connection* connection,