mojo/common: Decouple GURL dependency

mojo/common/url_type_converters.h

+// Copyright 2015 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_COMMON_URL_TYPE_CONVERTERS_H_
+#define MOJO_COMMON_URL_TYPE_CONVERTERS_H_
+
+#include "third_party/mojo/src/mojo/public/cpp/bindings/string.h"
+#include "third_party/mojo/src/mojo/public/cpp/bindings/type_converter.h"
+
+class GURL;
+
+namespace mojo {
+
+template <>
+struct TypeConverter<String, GURL> {
+  static String Convert(const GURL& input);
+};
+
+template <>
+struct TypeConverter<GURL, String> {
+  static GURL Convert(const String& input);
+};
+
+}  // namespace mojo
+
+#endif  // MOJO_COMMON_URL_TYPE_CONVERTERS_H_