Rename CancellationFlag to AtomicFlag.

base/synchronization/atomic_flag.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_SYNCHRONIZATION_CANCELLATION_FLAG_H_
-#define BASE_SYNCHRONIZATION_CANCELLATION_FLAG_H_
+#ifndef BASE_SYNCHRONIZATION_ATOMIC_FLAG_H_
+#define BASE_SYNCHRONIZATION_ATOMIC_FLAG_H_
 
 #include "base/atomicops.h"
 #include "base/base_export.h"
 #include "base/macros.h"
-#include "base/threading/platform_thread.h"
+#include "base/threading/thread_checker.h"
 
 namespace base {
 
-// CancellationFlag allows one thread to cancel jobs executed on some worker
-// thread. Calling Set() from one thread and IsSet() from a number of threads
-// is thread-safe.
+// A flag that can safely be set from one thread and read from other threads.
 //
 // This class IS NOT intended for synchronization between threads.
-class BASE_EXPORT CancellationFlag {
+class BASE_EXPORT AtomicFlag {
  public:
-  CancellationFlag() : flag_(false) {
-#if !defined(NDEBUG)
-    set_on_ = PlatformThread::CurrentId();
-#endif
-  }
-  ~CancellationFlag() {}
+  AtomicFlag();
+  ~AtomicFlag() = default;
 
-  // Set the flag. May only be called on the thread which owns the object.
+  // Set the flag. May only be called on the thread which created the object.
   void Set();
-  bool IsSet() const;  // Returns true iff the flag was set.
 
-  // For subtle reasons that may be different on different architectures,
-  // a different thread testing IsSet() may erroneously read 'true' after
-  // this method has been called.
+  // Returns true iff the flag was set.
+  bool IsSet() const;
+
+  // Resets the flag. Be careful when using this: callers might not expect
+  // IsSet() to return false after returning true once.
   void UnsafeResetForTesting();
 
  private:
-  base::subtle::Atomic32 flag_;
-#if !defined(NDEBUG)
-  PlatformThreadId set_on_;
-#endif
+  base::subtle::Atomic32 flag_ = 0;
+  ThreadChecker thread_checker_;
 
-  DISALLOW_COPY_AND_ASSIGN(CancellationFlag);
+  DISALLOW_COPY_AND_ASSIGN(AtomicFlag);
 };
 
 }  // namespace base
 
-#endif  // BASE_SYNCHRONIZATION_CANCELLATION_FLAG_H_
+#endif  // BASE_SYNCHRONIZATION_ATOMIC_FLAG_H_