Tab Search: Disable Verify ShowUI flaky test

Bug: 1148061
Change-Id: Ic3000705ca25b6d0ed48af4e1f8c323d67717722
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2533325
Commit-Queue: Thomas Lukaszewicz <tluk@chromium.org>
Commit-Queue: Roman Arora <romanarora@chromium.org>
Reviewed-by: Thomas Lukaszewicz <tluk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#826626}

chrome/test/data/webui/tab_search/tab_search_app_test.js

@@ -314,7 +314,10 @@ suite('TabSearchAppTest', () => {
         });
   });
 
-  test('Verify showUI() is called correctly', async () => {
+  /** TODO(crbug.com/1148061) Investigate/Fix flaky test. */
+  // Casting to avoid inexistent skip() function closure validation error.
+  /** @type {!Object} */
+  (test).skip('Verify showUI() is called correctly', async () => {
     assertEquals(0, testProxy.getCallCount('showUI'));
 
     await setupTest(sampleData());