Revert "[EventTiming] Add shadow DOM test for first input"

This reverts commit 9591b7074cacf1e8aeb9082dee2a4f46a171083f.

Reason for revert:
Failed blink_web_tests on webkit linux leak: https://ci.chromium.org/p/chromium/builders/ci/WebKit%20Linux%20Leak/13490:

({"numberOfLiveContextLifecycleStateObservers":[2,5],"numberOfLiveDocuments":[1,2],"numberOfLiveNodes":[4,21],"numberOfLiveResourceFetchers":[1,2],"numberOfLiveResources":[0,4]})

Original change's description:
> [EventTiming] Add shadow DOM test for first input
>
> This CL tests event.target for first-input. The DOM elements do not have
> event listeners to show that event retargetting correctly retargets to
> the shadow host.
>
> Bug: 543598
> Change-Id: Ibd5a4a37a50f79b86d93a5c9c18c8ac7300ba723
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2159622
> Reviewed-by: Steve Kobes <skobes@chromium.org>
> Commit-Queue: Nicolás Peña Moreno <npm@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#761417}

TBR=skobes@chromium.org,npm@chromium.org

Change-Id: I941e3f093e3d1fcba6662a54dec51b66690c9d70
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 543598
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2161125
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#761446}
diff --git a/event-timing/first-input-shadow-dom.html b/event-timing/first-input-shadow-dom.html
deleted file mode 100644
index 16279f0..0000000
--- a/event-timing/first-input-shadow-dom.html
+++ /dev/null
@@ -1,39 +0,0 @@
-<!DOCTYPE html>
-<html>
-<meta charset=utf-8 />
-<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>
-
-<body>
-<div id='container'>
-  <custom-button id='custom_button'></custom-button>
-</div>
-<script>
-async_test(function(t) {
-  assert_implements(window.PerformanceEventTiming, 'Event Timing is not supported.');
-  let innerButtonClicked = false;
-  customElements.define('custom-button', class extends HTMLElement {
-    connectedCallback() {
-      this.attachShadow({mode: 'open'});
-      this.shadowRoot.innerHTML = `<button id='inner_button_id'>Click me</button>`;
-      this.shadowRoot.getElementById('inner_button_id').onmousedown = () => {
-        innerButtonClicked = true;
-      };
-    }
-  });
-  const observer = new PerformanceObserver(t.step_func_done(entryList => {
-    // There must only be one first-input entry.
-    assert_equals(entryList.getEntries().length, 1);
-    // entry.target must be the shadow host due to retargetting.
-    assert_equals(entryList.getEntries()[0].target,
-        document.getElementById('custom_button'));
-    assert_true(innerButtonClicked, 'Did not reach the shadow DOM event listener!');
-  }));
-  observer.observe({entryTypes: ['first-input']});
-  test_driver.click(document.getElementById('custom_button'));
-}, "Event Timing: test first input on shadow DOM.");
-</script>
-</body>
-</html>