Fix the testharness async test API usage

third_party/WebKit/LayoutTests/shadow-dom/v0/pointer-lock-in-shadow2.html

Index: third_party/WebKit/LayoutTests/shadow-dom/v0/pointer-lock-in-shadow2.html
diff --git a/third_party/WebKit/LayoutTests/shadow-dom/v0/pointer-lock-in-shadow2.html b/third_party/WebKit/LayoutTests/shadow-dom/v0/pointer-lock-in-shadow2.html
index e39de0068754d4c96cdc94596227eab01b0eea9b..763d4a43984aae2af9cc7d2957dac31f27e62c15 100644
--- a/third_party/WebKit/LayoutTests/shadow-dom/v0/pointer-lock-in-shadow2.html
+++ b/third_party/WebKit/LayoutTests/shadow-dom/v0/pointer-lock-in-shadow2.html
@@ -20,12 +20,9 @@
 
 <script>
 async_test((test) => {
-    document.onpointerlockerror = () => {
-        assert_true(false, 'onpointerlockerror is not expected.');
-        test.done();
-    };
+    document.onpointerlockerror = test.unreached_func('onpointerlockerror is not expected.');
 
-    document.onpointerlockchange = () => {
+    document.onpointerlockchange = test.step_func(() => {
         // Not interested in handling before or after exitPointerLock.
         if (document.pointerLockElement === null)
             return;
@@ -37,15 +34,17 @@ async_test((test) => {
 
         document.exitPointerLock();
         test.done();
-    };
+    });
 
     convertTemplatesToShadowRootsWithin(host);
     var hostV1inV0 = hostV0.shadowRoot.querySelector('#hostV1inV0');
 
-    assert_equals(document.pointerLockElement, null);
-    assert_equals(host.shadowRoot.pointerLockElement, null);
-    assert_equals(hostV0.shadowRoot.pointerLockElement, null);
-    assert_equals(hostV1inV0.shadowRoot.pointerLockElement, null);
+    test.step(() => {
+        assert_equals(document.pointerLockElement, null);
+        assert_equals(host.shadowRoot.pointerLockElement, null);
+        assert_equals(hostV0.shadowRoot.pointerLockElement, null);
+        assert_equals(hostV1inV0.shadowRoot.pointerLockElement, null);
+    });
 
     var canvas = hostV1inV0.shadowRoot.querySelector('canvas');
     canvas.requestPointerLock();