Revert "Disable MigrationSingleClientTest tests due to flakiness"

This reverts commit 2c79a900.

Reason for revert: tests have stopped to fail and should have low
flakiness score now.

Original change's description:
> Disable MigrationSingleClientTest tests due to flakiness
>
> Tests disabled on Windows:
> - MigrationSingleClientTest.PrefsOnlyTriggerRefresh
> - MigrationSingleClientTest.PrefsOnlyModifyBookmark
>
> Bug: 1094907
> Change-Id: Ifba9e0a15138f4875ed6d2cb1ec1392b29b16c17
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2294859
> Commit-Queue: Rushan Suleymanov <rushans@google.com>
> Auto-Submit: Rushan Suleymanov <rushans@google.com>
> Reviewed-by: Maksim Moskvitin <mmoskvitin@google.com>
> Cr-Commit-Position: refs/heads/master@{#787685}

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

Bug: 1094907
Change-Id: Ic3a2e4e77d49aeaaf3de83aa701f7305b31d76e1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2317803Reviewed-by: Maksim Moskvitin <mmoskvitin@google.com>
Commit-Queue: Rushan Suleymanov <rushans@google.com>
Cr-Commit-Position: refs/heads/master@{#791789}

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

@@ -8,7 +8,6 @@
 #include "base/compiler_specific.h"
 #include "base/containers/circular_deque.h"
 #include "base/macros.h"
-#include "build/build_config.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/sync/test/integration/bookmarks_helper.h"
 #include "chrome/browser/sync/test/integration/migration_waiter.h"
@@ -230,26 +229,12 @@ IN_PROC_BROWSER_TEST_F(MigrationSingleClientTest, PrefsOnlyModifyPref) {
   RunSingleClientMigrationTest(MakeList(syncer::PREFERENCES), MODIFY_PREF);
 }
 
-// This is disabled due to flakiness: https://crbug.com/1094907.
-#if defined(OS_WIN)
-#define MAYBE_PrefsOnlyModifyBookmark DISABLED_PrefsOnlyModifyBookmark
-#else
-#define MAYBE_PrefsOnlyModifyBookmark PrefsOnlyModifyBookmark
-#endif
-IN_PROC_BROWSER_TEST_F(MigrationSingleClientTest,
-                       MAYBE_PrefsOnlyModifyBookmark) {
+IN_PROC_BROWSER_TEST_F(MigrationSingleClientTest, PrefsOnlyModifyBookmark) {
   RunSingleClientMigrationTest(MakeList(syncer::PREFERENCES),
                                MODIFY_BOOKMARK);
 }
 
-// This is disabled due to flakiness: https://crbug.com/1094907.
-#if defined(OS_WIN)
-#define MAYBE_PrefsOnlyTriggerRefresh DISABLED_PrefsOnlyTriggerRefresh
-#else
-#define MAYBE_PrefsOnlyTriggerRefresh PrefsOnlyTriggerRefresh
-#endif
-IN_PROC_BROWSER_TEST_F(MigrationSingleClientTest,
-                       MAYBE_PrefsOnlyTriggerRefresh) {
+IN_PROC_BROWSER_TEST_F(MigrationSingleClientTest, PrefsOnlyTriggerRefresh) {
   RunSingleClientMigrationTest(MakeList(syncer::PREFERENCES), TRIGGER_REFRESH);
 }