Better behavior if media doesn't support DRM scheme

We don't expect this case to occur, since track selection is
normally expected to check canAcquireSession before selecting
a track. Nevertheless, if an attempt is made to acquire a
session when the media doesn't support the manager's UUID, we
should fail in a more graceful way.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=173124170

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

@@ -26,6 +26,7 @@ import android.text.TextUtils;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.drm.DefaultDrmSession.ProvisioningManager;
 import com.google.android.exoplayer2.drm.DrmInitData.SchemeData;
+import com.google.android.exoplayer2.drm.DrmSession.DrmSessionException;
 import com.google.android.exoplayer2.drm.ExoMediaDrm.OnEventListener;
 import com.google.android.exoplayer2.extractor.mp4.PsshAtomUtil;
 import com.google.android.exoplayer2.util.Assertions;
@@ -372,19 +373,20 @@ public class DefaultDrmSessionManager<T extends ExoMediaCrypto> implements DrmSe
     if (offlineLicenseKeySetId == null) {
       SchemeData data = getSchemeData(drmInitData, uuid);
       if (data == null) {
+        final IllegalStateException error = new IllegalStateException(
+            "Media does not support uuid: " + uuid);
         if (eventHandler != null && eventListener != null) {
           eventHandler.post(new Runnable() {
             @Override
             public void run() {
-              eventListener.onDrmSessionManagerError(new IllegalStateException(
-                  "Media does not support uuid: " + uuid));
+              eventListener.onDrmSessionManagerError(error);
             }
           });
         }
-      } else {
-        initData = getSchemeInitData(data, uuid);
-        mimeType = getSchemeMimeType(data, uuid);
+        return new ErrorStateDrmSession<>(new DrmSessionException(error));
       }
+      initData = getSchemeInitData(data, uuid);
+      mimeType = getSchemeMimeType(data, uuid);
     }
 
     DefaultDrmSession<T> session;
@@ -414,6 +416,11 @@ public class DefaultDrmSessionManager<T extends ExoMediaCrypto> implements DrmSe
 
   @Override
   public void releaseSession(DrmSession<T> session) {
+    if (session instanceof ErrorStateDrmSession) {
+      // Do nothing.
+      return;
+    }
+
     DefaultDrmSession<T> drmSession = (DefaultDrmSession<T>) session;
     if (drmSession.release()) {
       sessions.remove(drmSession);

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

+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer2.drm;
+
+import com.google.android.exoplayer2.util.Assertions;
+import java.util.Map;
+
+/**
+ * A {@link DrmSession} that's in a terminal error state.
+ */
+/* package */ final class ErrorStateDrmSession<T extends ExoMediaCrypto> implements DrmSession<T> {
+
+  private final DrmSessionException error;
+
+  public ErrorStateDrmSession(DrmSessionException error) {
+    this.error = Assertions.checkNotNull(error);
+  }
+
+  @Override
+  public int getState() {
+    return STATE_ERROR;
+  }
+
+  @Override
+  public DrmSessionException getError() {
+    return error;
+  }
+
+  @Override
+  public T getMediaCrypto() {
+    return null;
+  }
+
+  @Override
+  public Map<String, String> queryKeyStatus() {
+    return null;
+  }
+
+  @Override
+  public byte[] getOfflineLicenseKeySetId() {
+    return null;
+  }
+
+}