Disable flaky PeriodicBackgroundSyncBrowserTest.FindATag

Tbr: nator@chromium.org
Bug: chromium:998466
Change-Id: I2ea87bbb861ec4ab77aa5a48905b6f8f0971c4b1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1774442Reviewed-by: Oskar Sundbom <ossu@chromium.org>
Commit-Queue: Oskar Sundbom <ossu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#691139}

content/browser/background_sync/periodic_background_sync_browsertest.cc

@@ -146,7 +146,7 @@ IN_PROC_BROWSER_TEST_F(PeriodicBackgroundSyncBrowserTest,
   EXPECT_TRUE(Unregister("foo"));
 }
 
-IN_PROC_BROWSER_TEST_F(PeriodicBackgroundSyncBrowserTest, FindATag) {
+IN_PROC_BROWSER_TEST_F(PeriodicBackgroundSyncBrowserTest, DISABLED_FindATag) {
   EXPECT_TRUE(RegisterServiceWorker());
   EXPECT_TRUE(LoadTestPage(kDefaultTestURL));  // Control the page.