Ahem (fix bad constant value).

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=124836700

library/src/main/java/com/google/android/exoplayer/drm/DrmSession.java

@@ -43,7 +43,7 @@ public interface DrmSession {
   /**
    * The session is open and has the keys required for decryption.
    */
-  int STATE_OPENED_WITH_KEYS = 3;
+  int STATE_OPENED_WITH_KEYS = 4;
 
   /**
    * Gets the current state of the session.