Sheriff: Disable flaky PrerenderIncognitoClosed test

This test is flaky on multiple platforms, so I'm disabling this test.

Example failure:
https://ci.chromium.org/p/chromium/builders/ci/linux-chromeos-rel/42845

TBR=ryansturm@chromium.org,adithyas@chromium.org

Bug: 994068
Change-Id: I1ca4f95ea9388e9eb7cb5184d0e821ee242ea91d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2537937Reviewed-by: Scott Little <sclittle@chromium.org>
Commit-Queue: Scott Little <sclittle@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827406}

chrome/browser/prefetch/no_state_prefetch/prerender_nostate_prefetch_browsertest.cc

@@ -1698,9 +1698,9 @@ IN_PROC_BROWSER_TEST_F(NoStatePrefetchIncognitoBrowserTest,
 }
 
 // Checks that prerenders are aborted when an incognito profile is closed.
-// ToDo(crbug.com/994068): The test is crashing on multiple platforms.
+// TODO(crbug.com/994068): The test is crashing on multiple platforms.
 IN_PROC_BROWSER_TEST_F(NoStatePrefetchIncognitoBrowserTest,
-                       PrerenderIncognitoClosed) {
+                       DISABLED_PrerenderIncognitoClosed) {
   std::unique_ptr<TestPrerender> test_prerender =
       PrefetchFromFile(kHungPrerenderPage, FINAL_STATUS_PROFILE_DESTROYED);
   current_browser()->window()->Close();