Load CMA backend from shared library

chromecast/media/base/key_systems_common.h

Index: chromecast/media/base/key_systems_common.h
diff --git a/chromecast/media/base/key_systems_common.h b/chromecast/media/base/key_systems_common.h
index 1537afd36ab1f21b3e42272fdcc3de05183eddae..53e323c60109a3007606bd6dcea981a551666b4e 100644
--- a/chromecast/media/base/key_systems_common.h
+++ b/chromecast/media/base/key_systems_common.h
@@ -10,6 +10,7 @@
 #include <vector>
 
 #include "base/compiler_specific.h"
+#include "chromecast/public/media/cast_key_system.h"
 #include "media/base/android/media_client_android.h"
 
 namespace chromecast {
@@ -19,13 +20,6 @@ namespace media {
 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);