Import wpt@c875b4212a473363afe8c09f012edf201386cb5b

third_party/WebKit/LayoutTests/resources/testharness.js

Index: third_party/WebKit/LayoutTests/resources/testharness.js
diff --git a/third_party/WebKit/LayoutTests/resources/testharness.js b/third_party/WebKit/LayoutTests/resources/testharness.js
index ceb3a4b462e4c664ade77b8a8916197dca5f6ac8..91dfab58c2b31e507092a71151f632fceb434825 100644
--- a/third_party/WebKit/LayoutTests/resources/testharness.js
+++ b/third_party/WebKit/LayoutTests/resources/testharness.js
@@ -471,6 +471,11 @@ policies and contribution forms [3].
             self instanceof ServiceWorkerGlobalScope) {
             return new ServiceWorkerTestEnvironment();
         }
+        if ('WorkerGlobalScope' in self &&
+            self instanceof WorkerGlobalScope) {
+            return new DedicatedWorkerTestEnvironment();
+        }
+
         throw new Error("Unsupported test environment");
     }