Add brotli content-encoding filter.

net/filter/brotli_filter.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.
+
+// BrotliFilter applies Brotli content decoding to a data
+// stream. Brotli format specification:
+// http://www.ietf.org/id/draft-alakuijala-brotli
+//
+// BrotliFilter is a subclass of Filter. See the latter's header file filter.h
+// for sample usage.
+
+#ifndef NET_FILTER_BROTLI_FILTER_H_
+#define NET_FILTER_BROTLI_FILTER_H_
+
+#include "net/filter/filter.h"
+
+namespace net {
+
+Filter* CreateBrotliFilter(Filter::FilterType type_id, int buffer_size);
+
+}  // namespace net
+
+#endif  // NET_FILTER_BROTLI_FILTER_H__