private boolean isSystemDownloadsProvider(final int uid) {
		final ProviderInfo provider = getPackageManager().resolveContentProvider("downloads", Apps.getFlagsMatchKnownPackages(this));
		if (provider == null) return false;
		final ApplicationInfo app_info = provider.applicationInfo;
		return (app_info.flags & FLAG_SYSTEM) != 0 && uid == app_info.uid;
	}
@param base_pkg the base package name for split APK installation, or null for full installation.
installer/src/main/java/com/oasisfeng/island/installer/AppInstallerActivity.java