升级考虑

1.如果只是替换/system/app 底下的某个应用，这个应用如果包含so 动态库的话，将不会升级该动态库，这个问题如何解决？
PackageManagerService.java 
        /* Note: We don't want to unpack the native binaries for
         *        system applications, unless they have been updated
         *        (the binaries are already under /system/lib).
         *        Also, don't unpack libs for apps on the external card
         *        since they should have their libraries in the ASEC
         *        container already.
         *
         *        In other words, we're going to unpack the binaries
         *        only for non-system apps and system app upgrades.
         */
        if (pkg.applicationInfo.nativeLibraryDir != null) {
            try {
                File nativeLibraryDir = new File(pkg.applicationInfo.nativeLibraryDir);
                final String dataPathString = dataPath.getCanonicalPath();


                if (isSystemApp(pkg) && !isUpdatedSystemApp(pkg)) {