Revive ApiLoader to enable updatable apk on Media2 APIs

package android.media.update;

import android.app.ActivityManager;

import android.app.AppGlobals;

import android.content.pm.ApplicationInfo;

import android.content.pm.PackageManager;

import android.content.pm.PackageManager.NameNotFoundException;

import android.os.Build;

import android.os.RemoteException;

import android.os.UserHandle;

import com.android.internal.annotations.GuardedBy;

import dalvik.system.PathClassLoader;

import java.io.File;

/**

 * @hide

 */

public final class ApiLoader {

    @GuardedBy("this")

    private static StaticProvider sMediaUpdatable;

    private static final String UPDATE_PACKAGE = "com.android.media.update";

    private static final String UPDATE_CLASS = "com.android.media.update.ApiFactory";

    private static final String UPDATE_METHOD = "initialize";

    private static final boolean REGISTER_UPDATE_DEPENDENCY = true;

    private ApiLoader() { }

    public static StaticProvider getProvider() {

        throw new RuntimeException("Use MediaSession/Browser instead of"

                + " hidden MediaSession2/Browser2 APIs.");

        try {

            return getMediaUpdatable();

        } catch (RemoteException e) {

            throw e.rethrowFromSystemServer();

        } catch (NameNotFoundException | ReflectiveOperationException e) {

            throw new RuntimeException(e);

        }

    }

    // TODO This method may do I/O; Ensure it does not violate (emit warnings in) strict mode.

    private static synchronized StaticProvider getMediaUpdatable()

            throws NameNotFoundException, ReflectiveOperationException, RemoteException {

        if (sMediaUpdatable != null) return sMediaUpdatable;

        // TODO Figure out when to use which package (query media update service)

        int flags = Build.IS_DEBUGGABLE ? 0 : PackageManager.MATCH_SYSTEM_ONLY;

        ApplicationInfo ai = AppGlobals.getPackageManager().getApplicationInfo(

                UPDATE_PACKAGE, flags, UserHandle.myUserId());

        if (REGISTER_UPDATE_DEPENDENCY) {

            // Register a dependency to the updatable in order to be killed during updates

            ActivityManager.getService().addPackageDependency(ai.packageName);

        }

        ClassLoader classLoader = new PathClassLoader(ai.sourceDir,

                ai.nativeLibraryDir + File.pathSeparator + System.getProperty("java.library.path"),

                ClassLoader.getSystemClassLoader().getParent());

        return sMediaUpdatable = (StaticProvider) classLoader.loadClass(UPDATE_CLASS)

                .getMethod(UPDATE_METHOD, ApplicationInfo.class).invoke(null, ai);

    }

}