Enable test PointerLockBrowserTest.PointerLockBasic

The tests in pointer_lock_browsertest.cc were flaky for 3 reasons:
- requestPointerLock being asynchronous
- mouse events being asynchronous
- native mouse events interfering with tests during execution
All the above were addressed in prior CLs.

Bug: 766450
Change-Id: Icc977b9c8bbfaba8c322a82ff6388886aee83941
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2212997Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Liviu Tinta <liviutinta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#772227}

content/browser/pointer_lock_browsertest.cc

@@ -212,8 +212,7 @@ const std::string PointerLockHelper::wait_for_pointer_lock_promise_ =
     "()=>false);})()";
 }  // namespace
 
-// crbug.com/1060129
-IN_PROC_BROWSER_TEST_F(PointerLockBrowserTest, DISABLED_PointerLockBasic) {
+IN_PROC_BROWSER_TEST_F(PointerLockBrowserTest, PointerLockBasic) {
   GURL main_url(embedded_test_server()->GetURL(
       "a.com", "/cross_site_iframe_factory.html?a(b)"));
   EXPECT_TRUE(NavigateToURL(shell(), main_url));