Disable flaky TabindexFocus test.

TBR=fukino@chromium.org

Bug: 833795
Change-Id: I105312fb6b0de0e2db8fad25b4463109e747e9e5
Reviewed-on: https://chromium-review.googlesource.com/1013942Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551306}

chrome/browser/chromeos/file_manager/file_manager_browsertest.cc

@@ -425,13 +425,8 @@ WRAPPED_INSTANTIATE_TEST_CASE_P(
     FileManagerBrowserTestWithLegacyEventDispatch,
     ::testing::Values(TestParameter(NOT_IN_GUEST_MODE, "searchBoxFocus")));
 
-#if defined(DISABLE_SLOW_FILESAPP_TESTS)
-#define MAYBE_TabindexFocus DISABLED_TabindexFocus
-#else
-#define MAYBE_TabindexFocus TabindexFocus
-#endif
 WRAPPED_INSTANTIATE_TEST_CASE_P(
-    MAYBE_TabindexFocus,
+    DISABLED_TabindexFocus,
     FileManagerBrowserTestWithLegacyEventDispatch,
     ::testing::Values(TestParameter(NOT_IN_GUEST_MODE, "tabindexFocus")));