Give the post-and-reply worker pool test a chance to finish on iOS

base/threading/worker_pool_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/threading/worker_pool.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/location.h"
 #include "base/message_loop.h"
@@ skipping 80 matching lines @@
 #endif
 
 TEST_F(WorkerPoolTest, MAYBE_PostTaskAndReply) {
   MessageLoop message_loop;
   scoped_refptr<PostTaskAndReplyTester> tester(new PostTaskAndReplyTester());
   tester->RunTest();
 
   const TimeDelta kMaxDuration = TestTimeouts::tiny_timeout();
   TimeTicks start = TimeTicks::Now();
   while (!tester->finished() && TimeTicks::Now() - start < kMaxDuration) {
+#if defined(OS_IOS)
+    // Ensure that the other thread has a chance to run even on a single-core
+    // device.
+    pthread_yield_np();
+#endif
     MessageLoop::current()->RunAllPending();
   }
   EXPECT_TRUE(tester->finished());
 }
 
 }  // namespace base