code: private void updateBundlesDirtyState(List<JoinableResourceBundle> bundles,
  			CssSmartSpritesResourceReader cssSpriteResourceReader) {
  
  		for (JoinableResourceBundle bundle : bundles) {
  
  			List<BundlePath> bundlePaths = bundle.getItemPathList();
  			for (BundlePath bundlePath : bundlePaths) {
  				String path = bundlePath.getPath();
  				File stdFile = cssSpriteResourceReader.getGeneratedCssFile(path);
  				File bckFile = cssSpriteResourceReader.getBackupFile(path);
  				if (bckFile.exists()) {
  					try {
  						if (!FileUtils.contentEquals(stdFile, bckFile)) {
  							bundle.setDirty(true);
  							break;
  						}
  					} catch (IOException e) {
  						throw new BundlingProcessException("Issue while generating smartsprite bundle", e);
  					}
  				}
  				cssSpriteResourceReader.getResource(bundle, path);
  			}
  		}
  	}
docs: Update the bundles dirty state
  
  @param bundles
  the list of bundle
  @param cssSpriteResourceReader
  the css sprite resource reader