Add brotli content-encoding filter.

net/http/http_features.cc

+// 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.
+
+#include "net/http/http_features.h"
+
+namespace net {
+
+namespace features {
+
+// Enables brotli "Accept-Encoding" advertising and "Content-Encoding" support.
+// Brotli format specification: http://www.ietf.org/id/draft-alakuijala-brotli
+const base::Feature kBrotliEncodingFeature = {
+    "brotli-encoding", base::FEATURE_DISABLED_BY_DEFAULT};
+
+bool IsBrotliEncodingEnabled() {
+#if !defined(DISABLE_BROTLI_SUPPORT)
+  return base::FeatureList::IsEnabled(kBrotliEncodingFeature);
+#else
+  return false;
+#endif
+}
+
+}  // namespace features
+
+}  // namespace net