Worker: Import "imported/wpt/workers" tests (Retry)

third_party/WebKit/LayoutTests/imported/wpt/workers/interfaces/DedicatedWorkerGlobalScope/EventTarget.worker.js

+importScripts("/resources/testharness.js");
+
+test(function(t) {
+    var i = 0;
+    addEventListener("message", function listener(evt) {
+        t.step(function() {
+            ++i;
+            removeEventListener("message", listener, true);
+        });
+    }, true);
+    self.dispatchEvent(new Event("message"));
+    self.dispatchEvent(new Event("message"));
+    assert_equals(i, 1);
+}, "removeEventListener");
+
+test(function() {
+    addEventListener("message", this.step_func(function(evt) {
+        assert_equals(evt.target, self);
+    }), true);
+    self.dispatchEvent(new Event("message"));
+}, "target");
+
+done();