Trim some superfluous imports.

import android.content.pm.Signature;

import android.net.Uri;

import android.os.Binder;

import android.os.Build;

import android.os.Bundle;

import android.os.Environment;

import android.os.Handler;

import java.io.EOFException;

import java.io.File;

import java.io.FileDescriptor;

import java.io.FileNotFoundException;

import java.io.IOException;

import java.io.PrintWriter;

import java.io.RandomAccessFile;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.HashSet;

import java.util.Iterator;

import java.util.List;

class BackupManagerService extends IBackupManager.Stub {