Add TareHandlerThread.

/*

 * Copyright (C) 2021 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.android.server.tare;

import android.os.HandlerThread;

import android.os.Looper;

import android.os.Trace;

/**

 * Singleton thread for all of TARE.

 *

 * @see com.android.internal.os.BackgroundThread

 */

final class TareHandlerThread extends HandlerThread {

    private static TareHandlerThread sInstance;

    private TareHandlerThread() {

        super("tare");

    }

    private static void ensureThreadLocked() {

        if (sInstance == null) {

            sInstance = new TareHandlerThread();

            sInstance.start();

            final Looper looper = sInstance.getLooper();

            looper.setTraceTag(Trace.TRACE_TAG_SYSTEM_SERVER);

        }

    }

    static TareHandlerThread get() {

        synchronized (TareHandlerThread.class) {

            ensureThreadLocked();

        }

        return sInstance;

    }

}