Revert of [cast_channel] Move cast_channel related files from //extensions to //components

components/cast_channel/proto/authority_keys.proto

Index: components/cast_channel/proto/authority_keys.proto
diff --git a/components/cast_channel/proto/authority_keys.proto b/components/cast_channel/proto/authority_keys.proto
deleted file mode 100644
index 9f62d200dc07ca12af3bb0542116ce72e5b5e3f1..0000000000000000000000000000000000000000
--- a/components/cast_channel/proto/authority_keys.proto
+++ /dev/null
@@ -1,17 +0,0 @@
-// Copyright 2014 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.
-
-syntax = "proto2";
-
-option optimize_for = LITE_RUNTIME;
-
-package cast_channel.proto;
-
-message AuthorityKeys {
-  message Key {
-    required bytes fingerprint = 1;
-    required bytes public_key = 2;
-  }
-  repeated Key keys = 1;
-}