Add API 31 sources

Test: None
Change-Id: Ie45894f7a232b2a15e2439b2527ca1813f334cc5

android/app/SynchronousUserSwitchObserver.java

diff --git a/android/app/SynchronousUserSwitchObserver.java b/android/app/SynchronousUserSwitchObserver.java
new file mode 100644
index 0000000..3a73888
--- /dev/null
+++ b/android/app/SynchronousUserSwitchObserver.java
@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2015 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 android.app;
+
+import android.os.Bundle;
+import android.os.IRemoteCallback;
+import android.os.RemoteException;
+
+/**
+ * Base class for synchronous implementations of {@link IUserSwitchObserver}
+ *
+ * @hide
+ */
+public abstract class SynchronousUserSwitchObserver extends UserSwitchObserver {
+    /**
+     * Calls {@link #onUserSwitching(int)} and notifies {@code reply} by calling
+     * {@link IRemoteCallback#sendResult(Bundle)}.
+     */
+    @Override
+    public final void onUserSwitching(int newUserId, IRemoteCallback reply) throws RemoteException {
+        try {
+            onUserSwitching(newUserId);
+        } finally {
+            if (reply != null) {
+                reply.sendResult(null);
+            }
+        }
+    }
+
+    /**
+     * Synchronous version of {@link IUserSwitchObserver#onUserSwitching(int, IRemoteCallback)}
+     */
+    public abstract void onUserSwitching(int newUserId) throws RemoteException;
+}