Chrome extension content scripts and iframe

You need to inject 2 content scripts:

"content_scripts": [
    {
      "matches": ["http://www.example.com/*"],
      "js": ["example.js"]
    },{
      "matches": ["http://www.rapidshare.com/*"],
      "all_frames": true,
      "js": ["rapidshare.js"]
    }
]

In order to transfer the link from one script to another you need to communicate through background page:

rapidshare.js:

chrome.runtime.sendMessage({url: "link"});

background.js:

chrome.runtime.onMessage.addListener(function(request, sender, sendResponse) {
    chrome.tabs.sendMessage(sender.tab.id, request);
    sendResponse({});
});

example.js:

chrome.runtime.onRequest.addListener(function(request, sender, sendResponse) {
    console.log("received url:", request.url);
    sendResponse({});
});