Add applyWallpaper to TorusEngine

package com.google.android.torus.core.engine

import android.app.WallpaperManager

import android.app.wallpaper.WallpaperDescription

import android.service.wallpaper.WallpaperService.Engine

import com.google.android.torus.core.wallpaper.LiveWallpaper

/**

 */

interface TorusEngine {

    /**

     * Called when the engine is created. You should load the assets and initialize the

     * resources here.

     * Called when the engine is created. You should load the assets and initialize the resources

     * here.

     *

     * IMPORTANT: When this function is called, the surface used to render the engine has to be

     * ready.

    fun create(isFirstActiveInstance: Boolean = true)

    /**

     * Called when the [TorusEngine] resumes.

     * Called when the event [Engine.onApplyWallpaper] is called.

     *

     * @see Engine.onApplyWallpaper

     */

    fun applyWallpaper(which: Int): WallpaperDescription? {

        return null

    }

    /** Called when the [TorusEngine] resumes. */

    fun resume()

    /**

     * Called when the [TorusEngine] is paused.

     */

    /** Called when the [TorusEngine] is paused. */

    fun pause()

    /**

    fun destroy(isLastActiveInstance: Boolean = true)

    /**

     * Called when the engine changes its destination flag. The destination indicates whether

     * the wallpaper is drawn on home screen, lock screen, or both. It is a combination of

     * Called when the engine changes its destination flag. The destination indicates whether the

     * wallpaper is drawn on home screen, lock screen, or both. It is a combination of

     * [WallpaperManager.FLAG_LOCK] and/or [WallpaperManager.FLAG_SYSTEM]

     */

    fun onWallpaperFlagsChanged(which: Int) {}

            if (wallpaperEngine is TorusTouchListener) setTouchEventsEnabled(true)

        }

        override fun onApplyWallpaper(which: Int): WallpaperDescription? {

            super.onApplyWallpaper(which)

            return wallpaperEngine.applyWallpaper(which)

        }

        override fun onSurfaceCreated(holder: SurfaceHolder) {

            super.onSurfaceCreated(holder)