mojo: Use TYPE_DEFAULT message-loop for browser-tests.

chrome/test/base/mash_browser_tests_main.cc

Index: chrome/test/base/mash_browser_tests_main.cc
diff --git a/chrome/test/base/mash_browser_tests_main.cc b/chrome/test/base/mash_browser_tests_main.cc
index e4c6fbe00f6827ced69a34d36416938ea39e414f..4fdff6f408fc0ee5a98794342b2935418d8cc413 100644
--- a/chrome/test/base/mash_browser_tests_main.cc
+++ b/chrome/test/base/mash_browser_tests_main.cc
@@ -121,7 +121,7 @@ std::unique_ptr<content::MojoShellConnection> CreateMojoShellConnection(
 }
 
 void StartChildApp(shell::mojom::ServiceRequest service_request) {
-  base::MessageLoop message_loop(base::MessageLoop::TYPE_UI);
+  base::MessageLoop message_loop(base::MessageLoop::TYPE_DEFAULT);
   base::RunLoop run_loop;
   mash::MashPackagedService service;
   std::unique_ptr<shell::ServiceContext> context =