Source:
private ExtendedCssTree parseResources(List<URL> resources, TreeLogger logger) throws UnableToCompleteException { List<SourceCode> sourceCodes = new ArrayList<SourceCode>(resources.size()); boolean css = ensureEitherCssOrGss(resources, logger); if (css && !doAutoConvert) { logger.log(Type.ERROR, "Your ClientBundle is referncing css files instead of gss. " + "You will need to either convert these files to gss using the " + "converter tool or turn on auto convertion in your gwt.xml file. " + "Note: Autoconversion will be removed after 2.7, you will need to move to gss." + "Add this line to your gwt.xml file to temporary avoid this:" + "<set-configuration-property name=\"CssResource.autoConvertCss\" value=\"true\" />"); throw new UnableToCompleteException(); } Set<String> extractContantNames = null; if (doAutoConvert && css) { extractContantNames = extractConstantNames(resources, logger); } for (URL stylesheet : resources) { if(css) { String gss = new Css2Gss(stylesheet, new PrintWriter(System.err), extractContantNames, true).toGss(); sourceCodes.add(new SourceCode(stylesheet.getFile(), gss)); } else { TreeLogger branchLogger = logger.branch(TreeLogger.DEBUG, "Parsing GSS stylesheet " + stylesheet.toExternalForm()); try { String fileContent = Resources.asByteSource(stylesheet).asCharSource(Charsets.UTF_8) .read(); sourceCodes.add(new SourceCode(stylesheet.getFile(), fileContent)); continue; } catch (IOException e) { branchLogger.log(TreeLogger.ERROR, "Unable to parse CSS", e); } throw new UnableToCompleteException(); } } CssTree tree; try { tree = new GssParser(sourceCodes).parse(); } catch (GssParserException e) { logger.log(TreeLogger.ERROR, "Unable to parse CSS", e); throw new UnableToCompleteException(); } List<String> permutationAxes = finalizeTree(tree); checkErrors(); return new ExtendedCssTree(tree, permutationAxes); }

Target:
private ExtendedCssTree parseResources(List<URL> resources, TreeLogger logger) throws UnableToCompleteException { List<SourceCode> sourceCodes = new ArrayList<SourceCode>(resources.size()); boolean css = ensureEitherCssOrGss(resources, logger); if (css && !allowLegacy) { logger.log(Type.ERROR, "Your ClientBundle is referencing css files instead of gss. " + "You will need to either convert these files to gss using the " + "converter tool or turn on auto convertion in your gwt.xml file. " + "Note: Autoconversion will be removed after 2.7, you will need to move to gss." + "Add this line to your gwt.xml file to temporary avoid this:" + "<set-configuration-property name=\"CssResource.legacy\" value=\"true\" />"); throw new UnableToCompleteException(); } if (css) { String concatenatedCss = concatCssFiles(resources, logger); String gss = convertToGss(concatenatedCss, logger); sourceCodes.add(new SourceCode("[auto-converted gss files]", gss)); } else { for (URL stylesheet : resources) { TreeLogger branchLogger = logger.branch(TreeLogger.DEBUG, "Parsing GSS stylesheet " + stylesheet.toExternalForm()); try { String fileContent = Resources.asByteSource(stylesheet).asCharSource(Charsets.UTF_8).read(); sourceCodes.add(new SourceCode(stylesheet.getFile(), fileContent)); continue; } catch (IOException e) { branchLogger.log(TreeLogger.ERROR, "Unable to parse CSS", e); } throw new UnableToCompleteException(); } } CssTree tree; try { tree = new GssParser(sourceCodes).parse(); } catch (GssParserException e) { logger.log(TreeLogger.ERROR, "Unable to parse CSS", e); throw new UnableToCompleteException(); } List<String> permutationAxes = finalizeTree(tree); checkErrors(); return new ExtendedCssTree(tree, permutationAxes); }