Examine source code of Dropbox

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#ffffff",
      "tab_background_text": "#0284cf"
    }
  },
  "version": "2.0",
  "name": "Dropbox",
  "manifest_version": 2,
  "description": "As a user and a big fan of the Dropbox services, I decided to create this nice persona to customize my Firefox. And, as usual, I'm here to share this to all of you guys!\n\nHope you like!!"
}