To use the cookies API, you must declare the "cookies" permission in your manifest, along with host permissions for any hosts whose cookies you want to access. For example:
{
"name": "My extension",
...
"permissions": [
"cookies",
"*://*.google.com"
],
...
}
You can find a simple example of using the cookies API in the examples/api/cookies directory. For other examples and for help in viewing the source code, see Samples.