Examine source code of save4me

{
  "manifest_version": 2,
  "name": "save4me",
  "short_name": "save4me",
  "version": "1.0.22",
  "description": "I will help you to never lose your links again.",
  "icons": {
    "16": "plugin/16x16.png",
    "48": "plugin/48x48.png",
    "128": "plugin/128x128.png"
  },
  "commands": {
    "save": {
      "suggested_key": {
        "default": "Ctrl+Shift+S",
        "mac": "Command+Shift+S"
      },
      "description": "Save the current page."
    },
    "_execute_action": {
      "suggested_key": {
        "windows": "Ctrl+Shift+S",
        "mac": "Command+Shift+S",
        "chromeos": "Ctrl+Shift+S",
        "linux": "Ctrl+Shift+S"
      }
    }
  },
  "permissions": [
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://*/*",
        "http://*/*"
      ],
      "js": [
        "inject.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "page_action": {
    "default_popup": "index.html",
    "default_icon": "plugin/48x48.png"
  },
  "browser_action": {
    "default_popup": "index.html",
    "default_icon": "plugin/48x48.png",
    "default_title": "Save4Me"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{e7fbfe0e-50ff-499c-8b96-4fd3c65dfca2}"
    }
  }
}