hum, if I understand ... you want to add an item to the menu after a right click?
You can do it:
chrome.contextMenus.create({ "title" : "You menu Name", "type" : "normal", "contexts" : ["link","video","audio"], //the context which item appear "onclick" : shorten() // The function call on click });
And your manifest:
Add "contextMenus" to the "permissions" array.
Additional information: here
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