Examine source code of Speedster

{
  "manifest_version": 2,
  "name": "Speedster",
  "version": "1.7",
  "description": "Control media playback speed with keyboard shortcuts allowing unlimited speed.",
  "permissions": [
    "activeTab",
    "<all_urls>",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "all_frames": true
    }
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icon48.png"
    }
  },
  "commands": {
    "increase-speed": {
      "suggested_key": {
        "default": "Alt+W"
      },
      "description": "Increase playback speed"
    },
    "decrease-speed": {
      "suggested_key": {
        "default": "Alt+X"
      },
      "description": "Decrease playback speed"
    },
    "reset-speed": {
      "suggested_key": {
        "default": "Alt+Z"
      },
      "description": "Reset or toggle last speed"
    }
  },
  "icons": {
    "48": "icon48.png",
    "96": "icon96.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{fc36ce8c-4b5f-48c6-809c-503d6a7e1007}"
    }
  }
}