Why am I Blocked from accessing a same-origin frame using "window.opener"?

I'm using Google Chrome and Adblock Plus.

Firstly, I opened http://ift.tt/LXtEj4 with Chrome and then open a console and input window.open("http://ift.tt/LXtEj4") in the console.

Then a new window will appear. I input window.opener.document in the new window's console, but it throws an error:

"Blocked a frame with origin "http://ift.tt/LXtEj4" from accessing a cross-origin frame."

I am quite confused because I'm using same-origin frame (Both window are from the same origin "http://ift.tt/LXtEj4") instead of cross-origin frame.. Why does the brower still complains about the Security Error?