Revert of Make the default ctor of rtc::Thread, protected

webrtc/rtc_base/criticalsection_unittest.cc

 /*
  *  Copyright 2014 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 183 matching lines @@
   static int AtomicOp(int* i) { return AtomicOps::Decrement(i); }
 };
 
 struct CompareAndSwapOp {
   static int AtomicOp(int* i) { return AtomicOps::CompareAndSwap(i, 0, 1); }
 };
 
 void StartThreads(std::vector<std::unique_ptr<Thread>>* threads,
                   MessageHandler* handler) {
   for (int i = 0; i < kNumThreads; ++i) {
-    std::unique_ptr<Thread> thread(Thread::Create());
+    std::unique_ptr<Thread> thread(new Thread());
     thread->Start();
     thread->Post(RTC_FROM_HERE, handler);
     threads->push_back(std::move(thread));
   }
 }
 
 }  // namespace
 
 TEST(AtomicOpsTest, Simple) {
   int value = 0;
@@ skipping 189 matching lines @@
   for (auto& t : threads)
     t.Start(&test_data, kThreadRepeats, 1);
 
   event.Wait(Event::kForever);
 
   for (auto& t : threads)
     t.Stop();
 }
 
 }  // namespace rtc