Make ThreadChecker::CalledOnValidThread() return true when called from the same task.

base/threading/thread_checker_impl.h

 // 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.
 
 #ifndef BASE_THREADING_THREAD_CHECKER_IMPL_H_
 #define BASE_THREADING_THREAD_CHECKER_IMPL_H_
 
 #include "base/base_export.h"
 #include "base/compiler_specific.h"
 #include "base/sequence_token.h"
@@ skipping 24 matching lines @@
   void EnsureAssigned() const;
 
   // Members are mutable so that CalledOnValidThread() can set them.
 
   // Synchronizes access to all members.
   mutable base::Lock lock_;
 
   // Thread on which CalledOnValidThread() may return true.
   mutable PlatformThreadRef thread_id_;
 
+  // TaskToken for which CalledOnValidThread() always returns true. This allows
+  // CalledOnValidThread() to return true when called multiple times from the
+  // same task, even if it's not running in a single-threaded context itself
+  // (allowing usage of ThreadChecker/NonThreadSafe objects on the stack in the
+  // scope of one-off tasks). Note: CalledOnValidThread() may return true even
+  // if the current TaskToken is not equal to this.
+  mutable TaskToken task_token_;
+
   // SequenceToken for which CalledOnValidThread() may return true. Used to
   // ensure that CalledOnValidThread() doesn't return true for TaskScheduler
   // tasks that happen to run on the same thread but weren't posted to the same
   // SingleThreadTaskRunner.
   mutable SequenceToken sequence_token_;
 };
 
 }  // namespace base
 
 #endif  // BASE_THREADING_THREAD_CHECKER_IMPL_H_