Update pointerevents test pointerevent_coordinates_when_locked.html (#16561)

* Update pointerevents/pointerlock/pointerevent_coordinates_when_locked.html

close #16406

* update test instruction
diff --git a/pointerevents/pointerlock/pointerevent_coordinates_when_locked.html b/pointerevents/pointerlock/pointerevent_coordinates_when_locked.html
index 9dfd5e1..a793272 100644
--- a/pointerevents/pointerlock/pointerevent_coordinates_when_locked.html
+++ b/pointerevents/pointerlock/pointerevent_coordinates_when_locked.html
@@ -3,7 +3,7 @@
     <head>
         <title>Pointer Events pointer lock tests</title>
         <meta name="viewport" content="width=device-width">
-        <link rel="stylesheet" type="text/css" href="/external/wpt/pointerevents/pointerevent_styles.css">
+        <link rel="stylesheet" type="text/css" href="../pointerevent_styles.css">
         <script src="/resources/testharness.js"></script>
         <script src="/resources/testharnessreport.js"></script>
         <script src="/resources/testdriver.js"></script>
@@ -36,21 +36,19 @@
                 var test_pointerEvent = setup_pointerevent_test("Test pointerevent coordinates when pointer is locked", ['mouse']);
                 var div1 = document.getElementById("target");
 
-                on_event(div1, 'pointerdown', function(event) {
+                on_event(div1, 'click', function(event) {
                     if (test_state == kStateInit)
                        div1.requestPointerLock();
-                });
-                on_event(div1, 'pointerup', function(event) {
-                    if (test_state == kStateLocked)
+                    else if (test_state == kStateLocked)
                         document.exitPointerLock();
                 });
                 on_event(div1, 'pointermove', function(event) {
                     if (test_state == kStateLocked) {
                         test_pointerEvent.step(function() {
-                            assert_equals(last_pointer_client_pos['x'], event.clientX)
-                            assert_equals(last_pointer_client_pos['y'], event.clientY)
-                            assert_equals(last_pointer_screen_pos['x'], event.screenX)
-                            assert_equals(last_pointer_screen_pos['y'], event.screenY)
+                            assert_equals(event.clientX, last_pointer_client_pos['x'], 'clientX')
+                            assert_equals(event.clientY, last_pointer_client_pos['y'], 'clientY')
+                            assert_equals(event.screenX, last_pointer_screen_pos['x'], 'screenX')
+                            assert_equals(event.screenY, last_pointer_screen_pos['y'], 'screenY')
                         });
                     } else {
                         last_pointer_client_pos = {'x': event.clientX, 'y': event.clientY}
@@ -63,6 +61,17 @@
                         test_pointerEvent.step(function() {
                             assert_equals(document.pointerLockElement, div1, "document.pointerLockElement should be div1.");
                         });
+
+                        var actions = new test_driver.Actions();
+                        pos_x = div1.offsetWidth / 2;
+                        pos_y = div1.offsetHeight / 2;
+                        for (var i = 0; i < 10; i++) {
+                            // Move left and up.
+                            pos_x += 10;
+                            pos_y -= 10;
+                            actions.pointerMove(pos_x, pos_y, {origin: div1});
+                        }
+                        actions.pointerDown().pointerUp().send();
                     } else if (test_state == kStateLocked) {
                         test_state = kStateUnlocked;
                         test_pointerEvent.step(function() {
@@ -72,18 +81,7 @@
                     }
                 });
 
-                var actions = new test_driver.Actions();
-                actions.pointerMove(/* x = */ 0, /* y = */ 0, {origin: div1}).pointerDown();
-
-                pos_x = div1.offsetWidth / 2;
-                pos_y = div1.offsetHeight / 2;
-                for (var i = 0; i < 10; i++) {
-                    // Alternatively move left/right and up/down.
-                    pos_x += ((-1)**i) * i * 10;
-                    pos_y -= ((-1)**i) * i * 10;
-                    actions.pointerMove(pos_x, pos_y, {origin: div1});
-                }
-                actions.pointerUp().send();
+                new test_driver.Actions().pointerMove(/* x = */ 0, /* y = */ 0, {origin: div1}).pointerDown().pointerUp().send();
             }
         </script>
     </head>
@@ -93,16 +91,16 @@
         <h4>
             Test Description: This test checks the pointer event coordinates stays unchanged when pointer is locked.
             <ol>
-                 <li>Press left button down on the green rectangle and hold it.</li>
-                 <li>Move the mouse inside the green rectangle.</li>
-                 <li>Release mouse button. </li>
+                 <li>Click left mouse button on the green rectangle.</li>
+                 <li>Move the mouse around.</li>
+                 <li>Click left mouse button again. </li>
             </ol>
             </ol>
 
             Test passes if the proper behavior of the events is observed.
         </h4>
         <div id="testContainer">
-            <div id="target" style="width:800px;height:250px;background:green"></div>
+            <div id="target" style="width:200px;height:200px;background:green"></div>
         </div>
         <div class="spacer"></div>
     </body>