Share link header parsing code between blink and content.

components/link_header_util/link_header_util.h

Index: components/link_header_util/link_header_util.h
diff --git a/components/link_header_util/link_header_util.h b/components/link_header_util/link_header_util.h
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+++ b/components/link_header_util/link_header_util.h
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+// 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 COMPONENTS_LINK_HEADER_UTIL_LINK_HEADER_UTIL_H_
+#define COMPONENTS_LINK_HEADER_UTIL_LINK_HEADER_UTIL_H_
+
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#include "base/macros.h"
+#include "base/optional.h"
+
+namespace link_header_util {
+
+using StringIteratorPair =
+    std::pair<std::string::const_iterator, std::string::const_iterator>;
+
+// Split a Link: header in its individual values. A single Link: header can
+// contain multiple values, which are comma separated. This method splits the
+// entire string into iterator pairs for the individual link values.
+// This is very similar to what net::HttpUtil::ValuesIterator does, except it
+// takes the special syntax of <> enclosed URLs into account.
+std::vector<StringIteratorPair> SplitLinkHeader(const std::string& header);
+
+// Parse an individual link header in its URL and parameters. |begin| and |end|
+// indicate the string to parse. If it is succesfully parsed as a link header
+// value this method returns true, sets |url| to the URL part of the link header
+// value and adds the parameters from the link header value to |params|.
+// If any error occurs parsing, this returns false (but might have also modified
+// |url| and/or |params|).
+bool ParseLinkHeaderValue(
+    std::string::const_iterator begin,
+    std::string::const_iterator end,
+    std::string* url,
+    std::unordered_map<std::string, base::Optional<std::string>>* params);
+
+}  // namespace link_header_util
+
+#endif  // COMPONENTS_LINK_HEADER_UTIL_LINK_HEADER_UTIL_H_