Examine source code of Speed Controller K

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "name": "__MSG_extName__",
  "version": "3.1.5",
  "description": "__MSG_desName__",
  "permissions": [
    "storage",
    "<all_urls>"
  ],
  "content_scripts": [
    {
      "all_frames": true,
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "popup.html"
  },
  "manifest_version": 2,
  "default_locale": "en",
  "commands": {
    "_execute_browser_action": {
      "suggested_key": {
        "mac": "Alt+Y",
        "linux": "Ctrl+Shift+J",
        "windows": "Ctrl+Shift+Y"
      }
    },
    "left": {
      "suggested_key": {
        "default": "Ctrl+Shift+Left",
        "mac": "Command+Shift+Left"
      },
      "description": "Decrease Speed"
    },
    "right": {
      "suggested_key": {
        "default": "Ctrl+Shift+Right",
        "mac": "Command+Shift+Right"
      },
      "description": "Increase Speed"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{8a60f772-1990-40cf-aaf4-e07be6de2d43}"
    }
  }
}