Tentatively re-enable SitePerProcessHitTestBrowserTest.TouchActionAckTimeout

A number of changes have landed recently that may eliminate the
flakieness seen in this test. This CL re-enables the test, but feel
free to revert this if the flakes continue.

Bug: 871062
Change-Id: Iad353f9aecbf2eb59c4831ef70658f08c13a47a9
Reviewed-on: https://chromium-review.googlesource.com/1217087Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Commit-Queue: James MacLean <wjmaclean@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590047}

content/browser/site_per_process_hit_test_browsertest.cc

@@ -1531,10 +1531,9 @@ void GiveItSomeTime(int t) {
 // Regression test for https://crbug.com/851644. The test passes as long as it
 // doesn't crash.
 // Touch action ack timeout is enabled on Android only.
-// Flaky, see https://crbug.com/871062.
 #if defined(OS_ANDROID)
 IN_PROC_BROWSER_TEST_P(SitePerProcessHitTestBrowserTest,
-                       DISABLED_TouchActionAckTimeout) {
+                       TouchActionAckTimeout) {
   GURL main_url(
       embedded_test_server()->GetURL("/frame_tree/page_with_janky_frame.html"));
   ASSERT_TRUE(NavigateToURL(shell(), main_url));