media: Move key_system_names to media/base/

media/cdm/key_system_names.cc

-// Copyright 2013 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 "media/cdm/key_system_names.h"
-
-namespace media {
-
-const char kClearKey[] = "org.w3.clearkey";
-const char kExternalClearKey[] = "org.chromium.externalclearkey";
-
-bool IsClearKey(const std::string& key_system) {
-  return key_system == kClearKey;
-}
-
-bool IsChildKeySystemOf(const std::string& key_system,
-                        const std::string& base) {
-  std::string prefix = base + '.';
-  return key_system.substr(0, prefix.size()) == prefix;
-}
-
-bool IsExternalClearKey(const std::string& key_system) {
-  return key_system == kExternalClearKey ||
-         IsChildKeySystemOf(key_system, kExternalClearKey);
-}
-
-}  // namespace media