Add missing generic types

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=134099118

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

@@ -37,6 +37,6 @@ public interface DrmSessionManager<T extends ExoMediaCrypto> {
   /**
    * Releases a {@link DrmSession}.
    */
-  void releaseSession(DrmSession drmSession);
+  void releaseSession(DrmSession<T> drmSession);
 
 }

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

@@ -40,7 +40,7 @@ import java.util.UUID;
  * A {@link DrmSessionManager} that supports streaming playbacks using {@link MediaDrm}.
  */
 @TargetApi(18)
-public class StreamingDrmSessionManager<T extends ExoMediaCrypto> implements DrmSessionManager,
+public class StreamingDrmSessionManager<T extends ExoMediaCrypto> implements DrmSessionManager<T>,
     DrmSession<T> {
 
   /**
@@ -268,7 +268,7 @@ public class StreamingDrmSessionManager<T extends ExoMediaCrypto> implements Drm
   }
 
   @Override
-  public void releaseSession(DrmSession session) {
+  public void releaseSession(DrmSession<T> session) {
     if (--openCount != 0) {
       return;
     }