Chromecast: guard PlayReady with C-define to prevent accidental use.

chromecast/media/base/key_systems_common.h

 // 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.
 
 #ifndef CHROMECAST_MEDIA_BASE_KEY_SYSTEMS_COMMON_H_
 #define CHROMECAST_MEDIA_BASE_KEY_SYSTEMS_COMMON_H_
 
 #include <string>
 
 namespace chromecast {
 namespace media {
 
+#if defined(PLAYREADY_CDM_AVAILABLE)
 extern const char kChromecastPlayreadyKeySystem[];
+#endif  // defined(PLAYREADY_CDM_AVAILABLE)
 
 enum CastKeySystem {
   KEY_SYSTEM_NONE = 0,
   KEY_SYSTEM_CLEAR_KEY,
   KEY_SYSTEM_PLAYREADY,
   KEY_SYSTEM_WIDEVINE
 };
 
 // Translates a key system string into a CastKeySystem, calling into the
 // platform for known key systems if needed.
 CastKeySystem GetKeySystemByName(const std::string& key_system_name);
 
 // Translates a platform-specific key system string into a CastKeySystem.
 // TODO(gunsch): Remove when prefixed EME is removed.
 CastKeySystem GetPlatformKeySystemByName(const std::string& key_system_name);
 
 }  // namespace media
 }  // namespace chromecast
 
 #endif  // CHROMECAST_MEDIA_BASE_KEY_SYSTEMS_COMMON_H_