Clarify naming for ClearKey DRM support

library/src/main/java/com/google/android/exoplayer2/C.java

@@ -444,11 +444,11 @@ public final class C {
   public static final UUID UUID_NIL = new UUID(0L, 0L);
 
   /**
-   * UUID for the
-   * <a href="https://w3c.github.io/encrypted-media/format-registry/initdata/cenc.html">CENC DRM
-   * scheme</a>.
+   * UUID for the ClearKey DRM scheme.
+   * <p>
+   * ClearKey is supported on Android devices running Android 5.0 (API Level 21) and up.
    */
-  public static final UUID CENC_UUID = new UUID(0x1077EFECC0B24D02L, 0xACE33C1E52E2FB4BL);
+  public static final UUID CLEARKEY_UUID = new UUID(0x1077EFECC0B24D02L, 0xACE33C1E52E2FB4BL);
 
   /**
    * UUID for the Widevine DRM scheme.

library/src/main/java/com/google/android/exoplayer2/drm/DefaultDrmSessionManager.java

@@ -341,10 +341,10 @@ public class DefaultDrmSessionManager<T extends ExoMediaCrypto> implements DrmSe
           schemeInitData = psshData;
         }
       }
-      if (Util.SDK_INT < 26 && C.CENC_UUID.equals(uuid)
+      if (Util.SDK_INT < 26 && C.CLEARKEY_UUID.equals(uuid)
           && (MimeTypes.VIDEO_MP4.equals(schemeMimeType)
           || MimeTypes.AUDIO_MP4.equals(schemeMimeType))) {
-        // Prior to API level 26 the CDM only accepted "cenc" as the scheme mime type.
+        // Prior to API level 26 the ClearKey CDM only accepted "cenc" as the scheme for MP4.
         schemeMimeType = CENC_SCHEME_MIME_TYPE;
       }
     }