Fix DefaultDrmSessionManager canAcquireSession for offline modes

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183102837

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

@@ -362,6 +362,10 @@ public class DefaultDrmSessionManager<T extends ExoMediaCrypto> implements DrmSe
 
   @Override
   public boolean canAcquireSession(@NonNull DrmInitData drmInitData) {
+    if (offlineLicenseKeySetId != null) {
+      // An offline license can be restored so a session can always be acquired.
+      return true;
+    }
     SchemeData schemeData = getSchemeData(drmInitData, uuid, true);
     if (schemeData == null) {
       if (drmInitData.schemeDataCount == 1 && drmInitData.get(0).matches(C.COMMON_PSSH_UUID)) {