Don't leak the WatcherThreadManager background thread.

base/threading/thread.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/thread.h"
 
 #include "base/bind.h"
 #include "base/lazy_instance.h"
 #include "base/location.h"
 #include "base/synchronization/waitable_event.h"
@@ skipping 244 matching lines @@
     running_ = false;
   }
 
   // Let the thread do extra cleanup.
   CleanUp();
 
 #if defined(OS_WIN)
   com_initializer.reset();
 #endif
 
-  // Assert that MessageLoop::QuitWhenIdle was called by ThreadQuitHelper.
-  DCHECK(GetThreadWasQuitProperly());
+  if (message_loop->type() != MessageLoop::TYPE_CUSTOM) {
+    // Assert that MessageLoop::QuitWhenIdle was called by ThreadQuitHelper.
+    // Don't check for custom message pumps, because their shutdown might not
+    // allow this.
+    DCHECK(GetThreadWasQuitProperly());
+  }
 
   // We can't receive messages anymore.
   // (The message loop is destructed at the end of this block)
   message_loop_ = nullptr;
 }
 
 }  // namespace base