Add brotli content-encoding filter.

content/public/common/content_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 "build/build_config.h"
 #include "content/public/common/content_features.h"
 
 namespace features {
 
 // All features in alphabetical order.
 
+// Enables brotli "Accept-Encoding" advertising and "Content-Encoding" support.
+// Brotli format specification: http://www.ietf.org/id/draft-alakuijala-brotli
+const base::Feature kBrotliEncoding = {
+    "brotli-encoding", base::FEATURE_DISABLED_BY_DEFAULT};
+
 // Downloads resumption will be controllable via a flag until it's enabled
 // permanently. See https://crbug.com/7648
 const base::Feature kDownloadResumption{"DownloadResumption",
                                         base::FEATURE_ENABLED_BY_DEFAULT};
 
 // The Experimental Framework for controlling access to API experiments.
 const base::Feature kExperimentalFramework{"ExperimentalFramework",
                                            base::FEATURE_DISABLED_BY_DEFAULT};
 
 #if defined(OS_ANDROID)
 // FeatureList definition for the Seccomp field trial.
 const base::Feature kSeccompSandboxAndroid{"SeccompSandboxAndroid",
                                            base::FEATURE_DISABLED_BY_DEFAULT};
 #endif
 
 }  // namespace features