Loading Google API Javascript Client Library into Chrome Extension

So far the only solution I’ve found is to first inject the script into the background html page like I did:

background.js (excerpt)

 var head = document.getElementsByTagName('head')[0];
 var script = document.createElement('script');
 script.type="text/javascript";
 script.src = "https://apis.google.com/js/client.js?onload=callbackFunction";
 head.appendChild(script);

And then to bypass the security warning, edit the manifest file (source):

manifest.json (excerpt)

"content_security_policy": "script-src 'self' https://apis.google.com; object-src 'self'"

However, note that bypassing the security only works for https links, and I also find it kind of hacky…any other solutions are welcome