Adjust silent-ignore.html test to ensure there is user-activation.

The test is testing the return code of vibration not being supported.
Some browsers (chromium) implement a user-activation check first. Ensure
that a click is simulated first before executing the rest of the test.

Change-Id: I960cb568be31b718f773a940271b9eb7d745416b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2110074
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Reviewed-by: Mustaq Ahmed <mustaq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#752054}

third_party/blink/web_tests/external/wpt/vibration/silent-ignore-expected.txt

-This is a testharness.js-based test.
-FAIL Calling vibrate returns true assert_true: vibrate() returns true when vibration is not supported expected true got false
-Harness: the test ran to completion.
-

third_party/blink/web_tests/external/wpt/vibration/silent-ignore.html

@@ -4,7 +4,7 @@
     <meta charset='utf-8'/>
     <title>Vibration API: test that calls to vibrate() are silently ignored when the device cannot vibrate</title>
     <link rel='author' title='Robin Berjon' href='mailto:robin@berjon.com'/>
-    <link rel='help' href='http://www.w3.org/TR/vibration/#methods'/>
+    <link rel='help' href='https://w3c.github.io/vibration/#dfn-perform-vibration'/>
     <meta name='flags' content='dom, no-vibrator'/>
     <meta name='assert' content='If the device does not provide a vibration mechanism, or it is disabled, the user agent must silently ignore any invocations of the vibrate() method.'/>
   </head>
@@ -16,13 +16,20 @@
       supporting this API but running on a device that cannot vibrate must silently ignore the
       call (we test that it doesn't throw).
     </p>
+    <button type="button" id="button">Click here if the device doesn't support vibration</button>
     <div id='log'></div>
     <script src='/resources/testharness.js'></script>
     <script src='/resources/testharnessreport.js'></script>
+    <script src='/resources/testdriver.js'></script>
+    <script src='/resources/testdriver-vendor.js'></script>
     <script>
       if (undefined !== navigator.vibrate) {
-          test(function () {
-              assert_true(navigator.vibrate(1000), "vibrate() returns true when vibration is not supported");
+          async_test(function (t) {
+              var target = document.getElementById('button');
+              target.addEventListener("click", t.step_func_done(function() {
+                  assert_true(navigator.vibrate(1000), "vibrate() returns true when vibration is not supported");
+              }));
+              test_driver.click(target).catch(t.unreached_func("click failed"));
           }, "Calling vibrate returns true");
       }
     </script>