Update from https://crrev.com/329939

base/mac/dispatch_source_mach.cc

Index: base/mac/dispatch_source_mach.cc
diff --git a/base/mac/dispatch_source_mach.cc b/base/mac/dispatch_source_mach.cc
new file mode 100644
index 0000000000000000000000000000000000000000..745c9dec7d1f19f48edb0f1e0172f45522e71005
--- /dev/null
+++ b/base/mac/dispatch_source_mach.cc
@@ -0,0 +1,62 @@
+// 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.
+
+#include "base/mac/dispatch_source_mach.h"
+
+namespace base {
+
+DispatchSourceMach::DispatchSourceMach(const char* name,
+                                       mach_port_t port,
+                                       void (^event_handler)())
+    // TODO(rsesek): Specify DISPATCH_QUEUE_SERIAL, in the 10.7 SDK. NULL
+    // means the same thing but is not symbolically clear.
+    : DispatchSourceMach(dispatch_queue_create(name, NULL),
+                         port,
+                         event_handler) {
+  // Since the queue was created above in the delegated constructor, and it was
+  // subsequently retained, release it here.
+  dispatch_release(queue_);
+}
+
+DispatchSourceMach::DispatchSourceMach(dispatch_queue_t queue,
+                                       mach_port_t port,
+                                       void (^event_handler)())
+    : queue_(queue),
+      source_(dispatch_source_create(DISPATCH_SOURCE_TYPE_MACH_RECV,
+          port, 0, queue_)),
+      source_canceled_(dispatch_semaphore_create(0)) {
+  dispatch_retain(queue);
+
+  dispatch_source_set_event_handler(source_, event_handler);
+  dispatch_source_set_cancel_handler(source_, ^{
+      dispatch_semaphore_signal(source_canceled_);
+  });
+}
+
+DispatchSourceMach::~DispatchSourceMach() {
+  Cancel();
+}
+
+void DispatchSourceMach::Resume() {
+  dispatch_resume(source_);
+}
+
+void DispatchSourceMach::Cancel() {
+  if (source_) {
+    dispatch_source_cancel(source_);
+    dispatch_release(source_);
+    source_ = NULL;
+
+    dispatch_semaphore_wait(source_canceled_, DISPATCH_TIME_FOREVER);
+    dispatch_release(source_canceled_);
+    source_canceled_ = NULL;
+  }
+
+  if (queue_) {
+    dispatch_release(queue_);
+    queue_ = NULL;
+  }
+}
+
+}  // namespace base