Allow ApplicationTestBase clients to avoid a default MessageLoop.

mojo/public/cpp/application/lib/application_test_base.cc

Index: mojo/public/cpp/application/lib/application_test_base.cc
diff --git a/mojo/public/cpp/application/lib/application_test_base.cc b/mojo/public/cpp/application/lib/application_test_base.cc
index 93eb3d0e5cf99239103c4719dad22eb191ca8edf..4ace9f566d38e5017f8ebb6225c7d14481fafa64 100644
--- a/mojo/public/cpp/application/lib/application_test_base.cc
+++ b/mojo/public/cpp/application/lib/application_test_base.cc
@@ -57,8 +57,10 @@ ApplicationDelegate* ApplicationTestBase::GetApplicationDelegate() {
 }
 
 void ApplicationTestBase::SetUpWithArgs(const Array<String>& args) {
-  // A run loop is needed for ApplicationImpl initialization and communication.
-  Environment::InstantiateDefaultRunLoop();
+  // A run loop is recommended for ApplicationImpl initialization and
+  // communication.
+  if (IsDefaultLoopEnabled())

[msw, 2014/12/16 15:40:32]

Hmm, I think all the current apptests would fail without instantiating the
default run loop for application impl init, but I guess
PipelineIntegrationTestBase already creates a base::MessageLoop for your new
PipelineIntegrationTestHost; I guess this is reasonable.

+    Environment::InstantiateDefaultRunLoop();
 
   // New applications are constructed for each test to avoid persisting state.
   application_impl_ = new ApplicationImpl(GetApplicationDelegate(),
@@ -75,7 +77,12 @@ void ApplicationTestBase::SetUp() {
 void ApplicationTestBase::TearDown() {
   SetShellHandle(application_impl_->UnbindShell());
   delete application_impl_;
-  Environment::DestroyDefaultRunLoop();
+  if (IsDefaultLoopEnabled())
+    Environment::DestroyDefaultRunLoop();
+}
+
+bool ApplicationTestBase::IsDefaultLoopEnabled() {
+  return true;
 }
 
 }  // namespace test