Add placeholder test for completion domain.

pkg/analysis_server/test/integration/completion_domain_inttest.dart

Index: pkg/analysis_server/test/integration/completion_domain_inttest.dart
diff --git a/pkg/analysis_server/test/integration/completion_domain_inttest.dart b/pkg/analysis_server/test/integration/completion_domain_inttest.dart
index 574d390c019faa8481d0f1715c920438c59fe169..bfb9238ab166c5b201b4cb319024f0ba31875a1f 100644
--- a/pkg/analysis_server/test/integration/completion_domain_inttest.dart
+++ b/pkg/analysis_server/test/integration/completion_domain_inttest.dart
@@ -44,6 +44,12 @@ main() {
       });
     });
   }
+
+  test_placeholder() {
+    // The unit test framework freaks out if there are no tests, so this is a
+    // placeholder until we have a passing test.
+    // TODO(paulberry): remove this.
+  }
 }
 
 main() {