bug 655942, factor some worker code of the diff view
bug 655942, factor some worker code of the diff view

Pike/elmo,mozilla/elmo,Pike/elmo,Pike/elmo,mozilla/elmo,AdrianGaudebert/elmo,Pike/elmo,AdrianGaudebert/elmo,mozilla/elmo,mozilla/elmo,AdrianGaudebert/elmo