Delete broken PriorityHandlerThread class

This class is unnecessary; you can simply pass a thread
priority to HandlerThread's own constructor. It's also
broken, since HandlerThread.run() immediately overrides
the priority being set!

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=153461225

library/core/src/main/java/com/google/android/exoplayer2/ExoPlayerImplInternal.java

@@ -32,7 +32,6 @@ import com.google.android.exoplayer2.trackselection.TrackSelector;
 import com.google.android.exoplayer2.trackselection.TrackSelectorResult;
 import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.MediaClock;
-import com.google.android.exoplayer2.util.PriorityHandlerThread;
 import com.google.android.exoplayer2.util.StandaloneMediaClock;
 import com.google.android.exoplayer2.util.TraceUtil;
 import java.io.IOException;
@@ -196,7 +195,7 @@ import java.io.IOException;
 
     // Note: The documentation for Process.THREAD_PRIORITY_AUDIO that states "Applications can
     // not normally change to this priority" is incorrect.
-    internalPlaybackThread = new PriorityHandlerThread("ExoPlayerImplInternal:Handler",
+    internalPlaybackThread = new HandlerThread("ExoPlayerImplInternal:Handler",
         Process.THREAD_PRIORITY_AUDIO);
     internalPlaybackThread.start();
     handler = new Handler(internalPlaybackThread.getLooper(), this);

library/core/src/main/java/com/google/android/exoplayer2/util/PriorityHandlerThread.java

-/*
- * Copyright (C) 2016 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.util;
-
-import android.os.HandlerThread;
-import android.os.Process;
-
-/**
- * A {@link HandlerThread} with a specified process priority.
- */
-public final 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();
-  }
-
-}