media config: expand is_encrypted to a struct.

media/base/media_util.h

Index: media/base/media_util.h
diff --git a/media/base/media_util.h b/media/base/media_util.h
index 4e53c9a0c0e611b4ea0c5b7ef5fb180308148f96..c7ddc8bb1ea2ec61f3f1906f0fb26cd110fd1cdc 100644
--- a/media/base/media_util.h
+++ b/media/base/media_util.h
@@ -8,6 +8,7 @@
 #include <stdint.h>
 #include <vector>
 
+#include "media/base/encryption_scheme.h"
 #include "media/base/media_export.h"
 
 namespace media {
@@ -16,6 +17,11 @@ namespace media {
 // constructed with empty extra data.
 MEDIA_EXPORT std::vector<uint8_t> EmptyExtraData();
 
+// The following helper functions return new instances of EncryptionScheme that
+// indicate widely used settings.
+MEDIA_EXPORT EncryptionScheme Unencrypted();
+MEDIA_EXPORT EncryptionScheme AesCtrEncryptionScheme();
+
 }  // namespace media
 
 #endif  // MEDIA_BASE_UTIL_H_