Move DispatchSourceMach from //sandbox/mac to //base/mac.

sandbox/mac/dispatch_source_mach.h

-// Copyright 2014 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 SANDBOX_MAC_DISPATCH_SOURCE_MACH_H_
-#define SANDBOX_MAC_DISPATCH_SOURCE_MACH_H_
-
-#include <dispatch/dispatch.h>
-
-#include "base/macros.h"
-#include "sandbox/sandbox_export.h"
-
-namespace sandbox {
-
-// This class encapsulates a MACH_RECV dispatch source. When this object is
-// destroyed, the source will be cancelled and it will wait for the source
-// to stop executing work. The source can run on either a user-supplied queue,
-// or it can create its own for the source.
-class SANDBOX_EXPORT DispatchSourceMach {
- public:
-  // Creates a new dispatch source for the |port| and schedules it on a new
-  // queue that will be created with |name|. When a Mach message is received,
-  // the |event_handler| will be called.
-  DispatchSourceMach(const char* name,
-                     mach_port_t port,
-                     void (^event_handler)());
-
-  // Creates a new dispatch source with the same semantics as above, but rather
-  // than creating a new queue, it schedules the source on |queue|.
-  DispatchSourceMach(dispatch_queue_t queue,
-                     mach_port_t port,
-                     void (^event_handler)());
-
-  // Cancels the source and waits for it to become fully cancelled before
-  // releasing the source.
-  ~DispatchSourceMach();
-
-  // Resumes the source. This must be called before any Mach messages will
-  // be received.
-  void Resume();
-
- private:
-  // Cancels the source, after which this class will no longer receive Mach
-  // messages. Calling this more than once is a no-op.
-  void Cancel();
-
-  // The dispatch queue used to service the source_.
-  dispatch_queue_t queue_;
-
-  // A MACH_RECV dispatch source.
-  dispatch_source_t source_;
-
-  // Semaphore used to wait on the |source_|'s cancellation in the destructor.
-  dispatch_semaphore_t source_canceled_;
-
-  DISALLOW_COPY_AND_ASSIGN(DispatchSourceMach);
-};
-
-}  // namespace sandbox
-
-#endif  // SANDBOX_MAC_DISPATCH_SOURCE_MACH_H_