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 65b44219b2540cfda0d94528acf450701136f6c6..d921a6d97b9d00038f049795a527f16b3a0c45fc 100644
--- a/mojo/services/tracing/tracing_app.cc
+++ b/mojo/services/tracing/tracing_app.cc
@@ -42,8 +42,12 @@ bool TracingApp::AcceptConnection(mojo::Connection* connection) {
   return true;
 }
 
-void TracingApp::ShellConnectionLost() {
+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.
   base::MessageLoop::current()->QuitWhenIdle();
+  return false;
 }
 
 void TracingApp::Create(mojo::Connection* connection,