Add a BarrierClosure.

base/barrier_closure_unittest.cc

Index: base/barrier_closure_unittest.cc
diff --git a/base/barrier_closure_unittest.cc b/base/barrier_closure_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..da381b130e4e16075d22844afae053457a2c841a
--- /dev/null
+++ b/base/barrier_closure_unittest.cc
@@ -0,0 +1,36 @@
+// Copyright (c) 2013 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/barrier_closure.h"
+
+#include "base/bind.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace {
+
+void Increment(int* count) { (*count)++; }
+
+TEST(BarrierClosureTest, RunImmediatelyForZeroClosures) {
+  int count = 0;
+  base::Closure doneClosure(base::Bind(&Increment, base::Unretained(&count)));
+
+  base::Closure barrierClosure = base::BarrierClosure(0, doneClosure);
+  EXPECT_EQ(1, count);
+}
+
+TEST(BarrierClosureTest, RunAfterNumClosures) {
+  int count = 0;
+  base::Closure doneClosure(base::Bind(&Increment, base::Unretained(&count)));
+
+  base::Closure barrierClosure = base::BarrierClosure(2, doneClosure);
+  EXPECT_EQ(0, count);
+
+  barrierClosure.Run();
+  EXPECT_EQ(0, count);
+
+  barrierClosure.Run();
+  EXPECT_EQ(1, count);
+}
+
+}  // namespace