Connected displays: use Robolectric for tests

import static org.mockito.Mockito.doAnswer;

import static org.mockito.Mockito.doReturn;

import static org.mockito.Mockito.spy;

import static org.robolectric.Shadows.shadowOf;

import android.content.Context;

import android.content.res.Resources;

import android.os.Handler;

import android.os.Message;

import android.os.RemoteException;

import android.view.Display.Mode;

import androidx.preference.PreferenceScreen;

import androidx.test.core.app.ApplicationProvider;

import com.android.server.testutils.TestHandler;

import com.android.settings.connecteddevice.display.ExternalDisplaySettingsConfiguration.DisplayListener;

import com.android.settings.flags.FakeFeatureFlagsImpl;

import org.mockito.Mock;

import org.mockito.MockitoAnnotations;

import java.util.ArrayDeque;

import java.util.List;

public class ExternalDisplayTestBase {

    FakeFeatureFlagsImpl mFlags = new FakeFeatureFlagsImpl();

    Context mContext;

    DisplayListener mListener;

    TestHandler mHandler = new TestHandler(null);

    TestHandler mHandler;

    PreferenceManager mPreferenceManager;

    PreferenceScreen mPreferenceScreen;

    List<DisplayDevice> mDisplays;

    static class TestHandler extends Handler {

        private final ArrayDeque<Message> mPending = new ArrayDeque<>();

        private final Handler mSubhandler;

        TestHandler(Handler subhandler) {

            mSubhandler = subhandler;

        }

        ArrayDeque<Message> getPendingMessages() {

            return mPending;

        }

        /**

         * Schedules to send the message upon next invocation of {@link #flush()}. This ignores the

         * time argument since our code doesn't meaningfully use it, but this is the most convenient

         * way to intercept both Message and Callback objects synchronously.

         */

        @Override

        public boolean sendMessageAtTime(Message msg, long uptimeMillis) {

            mPending.add(msg);

            return true;

        }

        void flush() {

            for (var msg : mPending) {

                mSubhandler.sendMessage(msg);

            }

            mPending.clear();

            shadowOf(mSubhandler.getLooper()).idle();

        }

    }

    /**

     * Setup.

     */

            doReturn(display).when(mMockedInjector).getDisplay(display.getId());

        }

        doReturn(mFlags).when(mMockedInjector).getFlags();

        mHandler = new TestHandler(mContext.getMainThreadHandler());

        doReturn(mHandler).when(mMockedInjector).getHandler();

        doReturn("").when(mMockedInjector).getSystemProperty(

                VIRTUAL_DISPLAY_PACKAGE_NAME_SYSTEM_PROPERTY);