localStorage in a Firefox extension

I am trying to access the localStorage of a page from a Firefox extension. My understanding is that content gives a reference to the window of the current page. When I try and access the localStorage for the page with content.localStorage, I think I am getting a reference to it. However, when I try content.localStorage.length, I get nothing.

Attached is the code in question.

var myExtension = {
    init: function() {
        var appcontent = document.getElementById("appcontent");   // browser
        if(appcontent)
            appcontent.addEventListener("DOMContentLoaded", myExtension.onPageLoad, true);
    },

    onPageLoad: function(aEvent) {
        var doc = aEvent.originalTarget;
        alert(content.localStorage) // alerts "[object XPCNativeWrapper [object Storage]]"
        alert(content.localStorage.length) // alerts nothing
    }
window.addEventListener("load", function() { myExtension.init(); }, false);

EDIT#1: More information.

try{
    alert(content.localStorage.getItem('todoData'))
    alert(content.localStorage.length)
} catch (e){
   alert(e)
}

The length is throwing the exception "[Exception... "Component is not available" nsresult: "0x80040111 (NS_ERROR_NOT_AVAILABLE)"

localStorage.length works when I have it on a standard web page in Firefox, but content.localStorage.length dose not work from the Firefox extension. Now I'm confused...