Revert "Reenable a test in TwoClientPreferencesSyncTest on CrOS"

This reverts commit 05048d0f.

Reason for revert: test is still flaky on chromeos, e.g.:
https://chromium-swarm.appspot.com/task?id=414c06e82ad5da10&refresh=10&show_raw=1

Original change's description:
> Reenable a test in TwoClientPreferencesSyncTest on CrOS
> 
> Recent changes (linked to the bug) are believed to have deflaked the
> test, so let's reenable it on all platforms.
> 
> Bug: 873902
> Change-Id: I9804fa4d83c3b1afb9b71356d134736b63b11298
> Reviewed-on: https://chromium-review.googlesource.com/c/1343083
> Reviewed-by: Mohamed Amir Yosef <mamir@chromium.org>
> Commit-Queue: Mikel Astiz <mastiz@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#609649}

TBR=mastiz@chromium.org,mamir@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 873902
Change-Id: I6dbf839b515dfc5e374f28b6197e73f1f23ffcac
Reviewed-on: https://chromium-review.googlesource.com/c/1346303Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Reviewed-by: Mohamed Amir Yosef <mamir@chromium.org>
Commit-Queue: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610039}

chrome/browser/sync/test/integration/two_client_preferences_sync_test.cc

@@ -8,6 +8,7 @@
 #include "base/macros.h"
 #include "base/strings/stringprintf.h"
 #include "base/test/metrics/histogram_tester.h"
+#include "build/build_config.h"
 #include "chrome/browser/sync/test/integration/feature_toggler.h"
 #include "chrome/browser/sync/test/integration/preferences_helper.h"
 #include "chrome/browser/sync/test/integration/profile_sync_service_harness.h"
@@ -139,8 +140,17 @@ IN_PROC_BROWSER_TEST_P(TwoClientPreferencesSyncTest,
   ASSERT_TRUE(ListPrefMatchChecker(prefs::kURLsToRestoreOnStartup).Wait());
 }
 
-IN_PROC_BROWSER_TEST_P(TwoClientPreferencesSyncTest,
-                       E2E_ENABLED(SingleClientEnabledEncryptionBothChanged)) {
+// Disabled due to flakiness on Chrome OS: https://crbug.com/873902.
+#if defined(OS_CHROMEOS)
+#define MAYBE_SingleClientEnabledEncryptionBothChanged \
+  DISABLED_SingleClientEnabledEncryptionBothChanged
+#else
+#define MAYBE_SingleClientEnabledEncryptionBothChanged \
+  SingleClientEnabledEncryptionBothChanged
+#endif
+IN_PROC_BROWSER_TEST_P(
+    TwoClientPreferencesSyncTest,
+    E2E_ENABLED(MAYBE_SingleClientEnabledEncryptionBothChanged)) {
   ASSERT_TRUE(SetupSync());
   ASSERT_TRUE(BooleanPrefMatchChecker(prefs::kHomePageIsNewTabPage).Wait());
   ASSERT_TRUE(StringPrefMatchChecker(prefs::kHomePage).Wait());