Request extensions prefs via the background page

Requesting chrome.storage from the devtools page only works when devtools is undocked, as per https://code.google.com/p/chromium/issues/detail?id=178618&q=devtools%20process%20docked&colspec=ID%20Pri%20M%20Iteration%20ReleaseBlock%20Cr%20Status%20Owner%20Summary%20OS%20Modified