Add WTF::makeCancellable

third_party/WebKit/Source/wtf/MakeCancellable.cpp

Index: third_party/WebKit/Source/wtf/MakeCancellable.cpp
diff --git a/third_party/WebKit/Source/wtf/MakeCancellable.cpp b/third_party/WebKit/Source/wtf/MakeCancellable.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..587e911c3a21df1bf694d1be63760f88a8394912
--- /dev/null
+++ b/third_party/WebKit/Source/wtf/MakeCancellable.cpp
@@ -0,0 +1,43 @@
+// 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 {
+
+FunctionCanceller::FunctionCanceller() = default;
+FunctionCanceller::~FunctionCanceller() = default;
+
+ScopedFunctionCanceller::ScopedFunctionCanceller() = default;
+ScopedFunctionCanceller::ScopedFunctionCanceller(PassRefPtr<FunctionCanceller> canceller)
+    : m_canceller(canceller)
+{
+    DCHECK(m_canceller);
+}
+
+ScopedFunctionCanceller::ScopedFunctionCanceller(ScopedFunctionCanceller&&) = default;
+ScopedFunctionCanceller& ScopedFunctionCanceller::operator=(ScopedFunctionCanceller&&) = default;
+
+ScopedFunctionCanceller::~ScopedFunctionCanceller()
+{
+    cancel();
+}
+
+void ScopedFunctionCanceller::detach()
+{
+    m_canceller = nullptr;
+}
+
+void ScopedFunctionCanceller::cancel()
+{
+    if (!m_canceller)
+        return;
+
+    m_canceller->cancel();
+    m_canceller = nullptr;
+}
+
+} // namespace WTF