Fix flakyness in PrefMemberTest::MoveToThread

base/prefs/public/pref_member_unittest.cc

 // Copyright (c) 2011 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/prefs/public/pref_member.h"
 
 #include "base/bind.h"
 #include "base/message_loop.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/thread.h"
@@ skipping 38 matching lines @@
 
   void FetchValue() {
     base::WaitableEvent event(true, false);
     ASSERT_TRUE(
         pref_thread_.message_loop_proxy()->PostTask(
             FROM_HERE,
             base::Bind(&GetPrefValueHelper::GetPrefValue, this, &event)));
     event.Wait();
   }
 
+  // The thread must be stopped on the main thread. GetPrefValueHelper being
+  // ref-counted, the destructor can be called from any thread.
+  void StopThread() {
+    pref_thread_.Stop();
+  }
+
   bool value() { return value_; }
 
  private:
   friend class base::RefCountedThreadSafe<GetPrefValueHelper>;
   ~GetPrefValueHelper() {}
 
   void GetPrefValue(base::WaitableEvent* event) {
     value_ = pref_.GetValue();
     event->Signal();
   }
@@ skipping 237 matching lines @@
 
   prefs.SetBoolean(kBoolPref, true);
 
   helper->FetchValue();
   EXPECT_TRUE(helper->value());
 
   helper->Destroy();
 
   helper->FetchValue();
   EXPECT_TRUE(helper->value());
+
+  helper->StopThread();
 }