Re-enable the PostDelayed TaskQueue test on all platforms except Windows.

webrtc/base/task_queue_unittest.cc

 /*
  *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 73 matching lines @@
 TEST(TaskQueueTest, PostFromQueue) {
   static const char kQueueName[] = "PostFromQueue";
   TaskQueue queue(kQueueName);
 
   Event event(false, false);
   queue.PostTask(
       [&event, &queue]() { queue.PostTask([&event]() { event.Set(); }); });
   EXPECT_TRUE(event.Wait(1000));
 }
 
-TEST(TaskQueueTest, DISABLED_PostDelayed) {
+// Currently flaky on Windows. See issue 6610.
+#if defined(WEBRTC_WIN)
+#define MAYBE_PostDelayed DISABLED_PostDelayed
+#else
+#define MAYBE_PostDelayed PostDelayed
+#endif
+TEST(TaskQueueTest, MAYBE_PostDelayed) {
   static const char kQueueName[] = "PostDelayed";
   TaskQueue queue(kQueueName);
 
   Event event(false, false);
   uint32_t start = Time();
   queue.PostDelayedTask(Bind(&CheckCurrent, kQueueName, &event, &queue), 100);
   EXPECT_TRUE(event.Wait(1000));
   uint32_t end = Time();
   EXPECT_GE(end - start, 100u);
   EXPECT_NEAR(end - start, 200u, 100u);  // Accept 100-300.
@@ skipping 144 matching lines @@
       queue.PostTask(NewClosure([&tasks_executed]() { ++tasks_executed; },
                                 [&tasks_cleaned_up]() { ++tasks_cleaned_up; }));
     event.Set();  // Unblock the first task.
   }
 
   EXPECT_GE(tasks_cleaned_up, tasks_executed);
   EXPECT_EQ(kTaskCount, tasks_cleaned_up);
 }
 
 }  // namespace rtc