Mojo C++ bindings: support mapping mojo string to WTF::String.

mojo/public/cpp/bindings/lib/wtf_string_serialization.h

+// 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.
+
+#ifndef MOJO_PUBLIC_CPP_BINDINGS_LIB_WTF_STRING_SERIALIZATION_H_
+#define MOJO_PUBLIC_CPP_BINDINGS_LIB_WTF_STRING_SERIALIZATION_H_
+
+#include <stddef.h>
+
+#include "mojo/public/cpp/bindings/lib/array_internal.h"
+#include "mojo/public/cpp/bindings/lib/bindings_serialization.h"
+
+namespace WTF {
+class String;
+
+size_t GetSerializedSize_(const WTF::String& input,
+                          mojo::internal::SerializationContext* context);
+void Serialize_(const WTF::String& input,
+                mojo::internal::Buffer* buffer,
+                mojo::internal::String_Data** output,
+                mojo::internal::SerializationContext* context);
+bool Deserialize_(mojo::internal::String_Data* input,
+                  WTF::String* output,
+                  mojo::internal::SerializationContext* context);
+
+}  // namespace WTF
+
+#endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_WTF_STRING_SERIALIZATION_H_