[ChromeOS] Disable DriveSpecific/FileManagerBrowserTest/Test.*

This test group (5 tests in all) flakes more often than desired on chromium
trys (the CQ). Disable them while the flake cause is being investigated.

Note: these tests are only built and run on ChromeOS. TODO(noel) once issue
829310 is resolved, this change can be reverted.

Bug: 829310
Change-Id: If6e30690d9076debfd988a1fa0d7c93575099a14
Reviewed-on: https://chromium-review.googlesource.com/1006746
Commit-Queue: Noel Gordon <noel@chromium.org>
Reviewed-by: Henrik Grunell <grunell@chromium.org>
Reviewed-by: Tatsuhisa Yamaguchi <yamaguchi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550143}

chrome/browser/chromeos/file_manager/file_manager_browsertest.cc

@@ -248,13 +248,9 @@ WRAPPED_INSTANTIATE_TEST_CASE_P(
                       "rectory")));
 
 // Fails on official build. http://crbug.com/429294
-#if defined(DISABLE_SLOW_FILESAPP_TESTS) || defined(OFFICIAL_BUILD)
-#define MAYBE_DriveSpecific DISABLED_DriveSpecific
-#else
-#define MAYBE_DriveSpecific DriveSpecific
-#endif
+// Disabled: too often flakey on chromium trys. http://crbug.com/829310
 WRAPPED_INSTANTIATE_TEST_CASE_P(
-    MAYBE_DriveSpecific,
+    DISABLED_DriveSpecific,
     FileManagerBrowserTest,
     ::testing::Values(
         TestParameter(NOT_IN_GUEST_MODE, "openSidebarOffline"),