1 files changed, 85 insertions, 0 deletions
diff --git a/chromium/base/threading/thread_checker.h b/chromium/base/threading/thread_checker.h
new file mode 100644
index 00000000000..5a8ef2261d7
--- /dev/null
+++ b/chromium/base/threading/thread_checker.h
@@ -0,0 +1,85 @@
+// 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.
+
+#ifndef BASE_THREADING_THREAD_CHECKER_H_
+#define BASE_THREADING_THREAD_CHECKER_H_
+
+// Apart from debug builds, we also enable the thread checker in
+// builds with DCHECK_ALWAYS_ON so that trybots and waterfall bots
+// with this define will get the same level of thread checking as
+// debug bots.
+//
+// Note that this does not perfectly match situations where DCHECK is
+// enabled.  For example a non-official release build may have
+// DCHECK_ALWAYS_ON undefined (and therefore ThreadChecker would be
+// disabled) but have DCHECKs enabled at runtime.
+#if (!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON))
+#define ENABLE_THREAD_CHECKER 1
+#else
+#define ENABLE_THREAD_CHECKER 0
+#endif
+
+#if ENABLE_THREAD_CHECKER
+#include "base/threading/thread_checker_impl.h"
+#endif
+
+namespace base {
+
+// Do nothing implementation, for use in release mode.
+//
+// Note: You should almost always use the ThreadChecker class to get the
+// right version for your build configuration.
+class ThreadCheckerDoNothing {
+ public:
+  bool CalledOnValidThread() const {
+    return true;
+  }
+
+  void DetachFromThread() {}
+};
+
+// ThreadChecker is a helper class used to help verify that some methods of a
+// class are called from the same thread. It provides identical functionality to
+// base::NonThreadSafe, but it is meant to be held as a member variable, rather
+// than inherited from base::NonThreadSafe.
+//
+// While inheriting from base::NonThreadSafe may give a clear indication about
+// the thread-safety of a class, it may also lead to violations of the style
+// guide with regard to multiple inheritence. The choice between having a
+// ThreadChecker member and inheriting from base::NonThreadSafe should be based
+// on whether:
+//  - Derived classes need to know the thread they belong to, as opposed to
+//    having that functionality fully encapsulated in the base class.
+//  - Derived classes should be able to reassign the base class to another
+//    thread, via DetachFromThread.
+//
+// If neither of these are true, then having a ThreadChecker member and calling
+// CalledOnValidThread is the preferable solution.
+//
+// Example:
+// class MyClass {
+//  public:
+//   void Foo() {
+//     DCHECK(thread_checker_.CalledOnValidThread());
+//     ... (do stuff) ...
+//   }
+//
+//  private:
+//   ThreadChecker thread_checker_;
+// }
+//
+// In Release mode, CalledOnValidThread will always return true.
+#if ENABLE_THREAD_CHECKER
+class ThreadChecker : public ThreadCheckerImpl {
+};
+#else
+class ThreadChecker : public ThreadCheckerDoNothing {
+};
+#endif  // ENABLE_THREAD_CHECKER
+
+#undef ENABLE_THREAD_CHECKER
+
+}  // namespace base
+
+#endif  // BASE_THREADING_THREAD_CHECKER_H_