Disable ServiceWorkerFetchDispatcherBrowserTest.FetchEventTimeout due to flakes.

BUG=1156091
TBR=shimazu@chromium.org

Change-Id: I35d67c44693c0e3e9da3371a1b1a657f978c3d55
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2574950Reviewed-by: Greg Thompson <grt@chromium.org>
Commit-Queue: Greg Thompson <grt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#834213}

content/browser/service_worker/service_worker_fetch_dispatcher_browsertest.cc

@@ -241,8 +241,9 @@ IN_PROC_BROWSER_TEST_F(ServiceWorkerFetchDispatcherBrowserTest, FetchEvent) {
 // This is the timeout case that the lifetime of a fetch event is shorter than
 // the response finishes. ServiceWorkerFetchDispatcher::OnFetchEventFinished is
 // called first.
+// Disabled due to flakes; see https://crbug.com/1156091.
 IN_PROC_BROWSER_TEST_F(ServiceWorkerFetchDispatcherBrowserTest,
-                       FetchEventTimeout) {
+                       DISABLED_FetchEventTimeout) {
   StartServerAndNavigateToSetup();
   ServiceWorkerVersion* version = CreateVersion();