Update test scripts to run under the Dart 1.6 vm.

tools/testing/dart/http_server.dart

Index: tools/testing/dart/http_server.dart
diff --git a/tools/testing/dart/http_server.dart b/tools/testing/dart/http_server.dart
index f686e24eb2cf078f49f8d5b136b3d34c71e3bad2..36ddb25bcec4de777c7bff87957c5a76a5c987b7 100644
--- a/tools/testing/dart/http_server.dart
+++ b/tools/testing/dart/http_server.dart
@@ -366,6 +366,7 @@ class TestingServers {
     } else if (path.filename.endsWith('.dart')) {
       response.headers.set('Content-Type', 'application/dart');
     }
+    response.headers.removeAll("X-Frame-Options");
     file.openRead().pipe(response).catchError((e) {
       DebugLogger.warning(
           'HttpServer: error while closing the response stream', e);