Add missing class.

library/src/main/java/com/google/android/exoplayer/util/PriorityHandlerThread.java

+/*
+ * Copyright (C) 2014 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.exoplayer.util;
+
+import android.os.HandlerThread;
+import android.os.Process;
+
+/**
+ * A {@link HandlerThread} with a specified process priority.
+ */
+public class PriorityHandlerThread extends HandlerThread {
+
+  private final int priority;
+
+  /**
+   * @param name The name of the thread.
+   * @param priority The priority level. See {@link Process#setThreadPriority(int)} for details.
+   */
+  public PriorityHandlerThread(String name, int priority) {
+    super(name);
+    this.priority = priority;
+  }
+
+  @Override
+  public void run() {
+    Process.setThreadPriority(priority);
+    super.run();
+  }
+
+}