Add WTF::makeCancellable

third_party/WebKit/Source/wtf/MakeCancellable.cpp

+// Copyright 2016 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 "wtf/MakeCancellable.h"
+
+#include "base/logging.h"
+
+namespace WTF {
+namespace internal {
+
+FunctionCancellerImplBase::FunctionCancellerImplBase() = default;
+FunctionCancellerImplBase::~FunctionCancellerImplBase() = default;
+
+} // namespace internal
+
+FunctionCanceller::FunctionCanceller() = default;
+FunctionCanceller::FunctionCanceller(PassRefPtr<internal::FunctionCancellerImplBase> cancellation)
+    : m_cancellation(cancellation)
+{
+    DCHECK(m_cancellation);
+}
+
+FunctionCanceller::FunctionCanceller(FunctionCanceller&&) = default;
+FunctionCanceller& FunctionCanceller::operator=(FunctionCanceller&&) = default;
+
+FunctionCanceller::~FunctionCanceller()
+{
+    cancel();
+}
+
+void FunctionCanceller::detach()
+{
+    m_cancellation = nullptr;
+}
+
+void FunctionCanceller::cancel()
+{
+    if (!m_cancellation)
+        return;
+
+    m_cancellation->cancel();
+    m_cancellation = nullptr;
+}
+
+} // namespace WTF