Add new HTTP/2 and HPACK decoder in net/http2/.

net/http2/hpack/http2_hpack_constants.h

Index: net/http2/hpack/http2_hpack_constants.h
diff --git a/net/http2/hpack/http2_hpack_constants.h b/net/http2/hpack/http2_hpack_constants.h
new file mode 100644
index 0000000000000000000000000000000000000000..b9883a01cf7215c852f01c039324020fdac1eae9
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+++ b/net/http2/hpack/http2_hpack_constants.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 NET_HTTP2_HPACK_HTTP2_HPACK_CONSTANTS_H_
+#define NET_HTTP2_HPACK_HTTP2_HPACK_CONSTANTS_H_
+
+// Enum HpackEntryType identifies the 5 basic types of HPACK Block Entries.
+//
+// See the spec for details:
+// https://http2.github.io/http2-spec/compression.html#rfc.section.6
+
+#include <ostream>
+#include <string>
+
+#include "net/base/net_export.h"
+
+namespace net {
+
+enum class HpackEntryType {
+  // Entry is an index into the static or dynamic table. Decoding it has no
+  // effect on the dynamic table.
+  kIndexedHeader,
+
+  // The entry contains a literal value. The name may be either a literal or a
+  // reference to an entry in the static or dynamic table.
+  // The entry is added to the dynamic table after decoding.
+  kIndexedLiteralHeader,
+
+  // The entry contains a literal value. The name may be either a literal or a
+  // reference to an entry in the static or dynamic table.
+  // The entry is not added to the dynamic table after decoding, but a proxy
+  // may choose to insert the entry into its dynamic table when forwarding
+  // to another endpoint.
+  kUnindexedLiteralHeader,
+
+  // The entry contains a literal value. The name may be either a literal or a
+  // reference to an entry in the static or dynamic table.
+  // The entry is not added to the dynamic table after decoding, and a proxy
+  // must NOT insert the entry into its dynamic table when forwarding to another
+  // endpoint.
+  kNeverIndexedLiteralHeader,
+
+  // Entry conveys the size limit of the dynamic table of the encoder to
+  // the decoder. May be used to flush the table by sending a zero and then
+  // resetting the size back up to the maximum that the encoder will use
+  // (within the limits of SETTINGS_HEADER_TABLE_SIZE sent by the
+  // decoder to the encoder, with the default of 4096 assumed).
+  kDynamicTableSizeUpdate,
+};
+
+// Returns the name of the enum member.
+NET_EXPORT_PRIVATE std::string HpackEntryTypeToString(HpackEntryType v);
+
+// Inserts the name of the enum member into |out|.
+NET_EXPORT_PRIVATE std::ostream& operator<<(std::ostream& out,
+                                            HpackEntryType v);
+
+}  // namespace net
+
+#endif  // NET_HTTP2_HPACK_HTTP2_HPACK_CONSTANTS_H_