Implement a trivial Mojo EchoService that can be connected to over DBus

mojo/shell/context.cc

Index: mojo/shell/context.cc
diff --git a/mojo/shell/context.cc b/mojo/shell/context.cc
index 2ba4aef4f14adf8f60d001c3fa48d5facb33f878..223f87bc47b2502ec6f9e795a7ebd6e2d9c0d8a7 100644
--- a/mojo/shell/context.cc
+++ b/mojo/shell/context.cc
@@ -10,6 +10,7 @@
 #include "mojo/service_manager/service_loader.h"
 #include "mojo/service_manager/service_manager.h"
 #include "mojo/services/native_viewport/native_viewport_service.h"
+#include "mojo/shell/dbus_service_loader.h"
 #include "mojo/shell/dynamic_service_loader.h"
 #include "mojo/shell/in_process_dynamic_service_runner.h"
 #include "mojo/shell/network_delegate.h"
@@ -66,6 +67,9 @@ Context::Context()
   service_manager_.SetLoaderForURL(native_viewport_service_loader_.get(),
                                     GURL("mojo:mojo_native_viewport_service"));
 
+  dbus_service_loader_.reset(new DBusServiceLoader(this));
+  service_manager_.SetLoaderForScheme(dbus_service_loader_.get(), "dbus");
+
   if (cmdline->HasSwitch(switches::kSpy)) {
     spy_.reset(new mojo::Spy(&service_manager_,
                              cmdline->GetSwitchValueASCII(switches::kSpy)));