Content script jQuery dynamic include broken?

I don't want to include jQuery on every page by listing it in the manifest

In the console, this works fine, but I can't dynamically include jQuery in a content script

No idea why

1. Put these two files in a folder (content.js and manifest.json)
2. Go to chrome:extensions in omnibox (url bar)
3. Load Unpacked Extension
4. Select Folder
5. Go to any page and CMD+Shift+R reload without cache

Check out the console and see jQuery is undefined

content.js

if (document.readyState === "complete") {
    appendJQuery();
} else {
    document.addEventListener("DOMContentLoaded", appendJQuery);
} function appendJQuery () {
    var jq = document.createElement("script");
    window.document.querySelector("head").appendChild(jq);
    jq.onload = function () {
        console.log(typeof $); // $ is not defined ?????
    }
    jq.src = "https://code.jquery.com/jquery-2.1.1.min.js";
}

manifest.json

{
    "manifest_version": 2,
    "name": "Sample",
    "short_name": "Sample",
    "version": "1.1",
    "permissions": ["tabs", "http://*/*, https://*/*", "*://*/*", "<all_urls>"],
    "content_scripts": [{
        "matches": ["*://*/*", "http://*/*", "https://*/*", "file://*/*"],
        "js": ["content.js"],
        "run_at": "document_start"
    }]
}

then jQuery is undefined......... wtf??? anyone know why??