Display a pause screen in a paused browser.

lib/src/runner/vm/environment.dart

Index: lib/src/runner/vm/environment.dart
diff --git a/lib/src/runner/vm/environment.dart b/lib/src/runner/vm/environment.dart
index 9833d81806d1fdddeb9a9166ee684d1c0320402d..bbe341817fa1c797185483c3ac6897f3e2a18efb 100644
--- a/lib/src/runner/vm/environment.dart
+++ b/lib/src/runner/vm/environment.dart
@@ -5,8 +5,13 @@
 library test.runner.vm.environment;
 
 import '../environment.dart';
+import '../../util/cancelable_future.dart';
 
 /// The environment for test suites loaded in an isolate in this Dart VM.
 class VMEnvironment implements Environment {
   const VMEnvironment();
+
+  CancelableFuture displayPause() =>
+      throw new UnsupportedError(
+          "The VM doesn't yet support Environment.displayPause.");
 }