Just paste this as URL of the browser tab:

data:text/html, <title>Text Editor</title><body contenteditable style="font-size:2rem;line-height:1.4;max-width:60rem;margin:0 auto;padding:4rem;">

 

Exteded version: 

data:text/html;charset=utf-8, <title>TextEditor</title> <link rel="shortcut icon" href="http://g.etfv.co/https://docs.google.com"/> <style> html{height: 100%;} body{background: -webkit-linear-gradient(#f0f0f0, #fff); padding: 3%; height: 94%;} .paper { font: normal 12px/1.5 "Lucida Grande", arial, sans-serif; width: 50%; height: 80%; margin: 0 auto; padding: 6px 5px 4px 42px; position: relative; color: #444; line-height: 20px; border: 1px solid #d2d2d2; background: #fff; background: -webkit-gradient(linear, 0 0, 0 100%, from(#d9eaf3), color-stop(4%, #fff)) 0 4px; background: -webkit-linear-gradient(top, #d9eaf3 0%, #fff 8%) 0 4px; background: -moz-linear-gradient(top, #d9eaf3 0%, #fff 8%) 0 4px; background: -ms-linear-gradient(top, #d9eaf3 0%, #fff 8%) 0 4px; background: -o-linear-gradient(top, #d9eaf3 0%, #fff 8%) 0 4px; background: linear-gradient(top, #d9eaf3 0%, #fff 8%) 0 4px; -webkit-background-size: 100% 20px; -moz-background-size: 100% 20px; -ms-background-size: 100% 20px; -o-background-size: 100% 20px; background-size: 100% 20px; -webkit-border-radius: 3px; -moz-border-radius: 3px; border-radius: 3px; -webkit-box-shadow: 0 1px 2px rgba(0,0,0,0.07); -moz-box-shadow: 0 1px 2px rgba(0,0,0,0.07); box-shadow: 0 1px 2px rgba(0,0,0,0.07); } .paper::before { content: ''; position: absolute; width: 4px; top: 0; left: 30px; bottom: 0; border: 1px solid; border-color: transparent #efe4e4; } textarea{display: block; width:94%;margin:0 auto;padding:3.8% 3%; border: none; outline: none; height: 94%; background: transparent; line-height: 20px;} </style> <body spellcheck="false"> <div class="paper"> <textarea autofocus="autofocus"></textarea> </div> </body> </html>

 

Took the best bits (IMHO) from all the code above:
– Paper styling.
– Auto focus.
– No TextEdit field (so Ctrl+S works).
– Fav icon from google docs.
– Slightly larger font.
– Spell checking on (easy to turn off if you like) 

 

 

data:text/html;charset=utf-8, <title>TextEditor</title>
       
<style>
body {
        background: -webkit-linear-gradient(#f0f0f0, #fff);
        padding: 3%;
        height: 94%;
       
}
 
.paper {
        font: normal 14px "Lucida Grande", arial, sans-serif;
        width: 50%;
        height: 80%;
        margin: 0 auto;
        padding: 6px 5px 4px 42px;
        position: relative;
        color: #444;
        line-height: 20px;
        border: 1px solid #d2d2d2;
        background: #fff;
        background: -webkit-gradient(linear, 0 0, 0 100%, from(#d9eaf3), color-stop(4%, #fff)) 0 4px;
        background: -webkit-linear-gradient(top, #d9eaf3 0%, #fff 8%) 0 4px;
        background: -moz-linear-gradient(top, #d9eaf3 0%, #fff 8%) 0 4px;
        background: -ms-linear-gradient(top, #d9eaf3 0%, #fff 8%) 0 4px;
        background: -o-linear-gradient(top, #d9eaf3 0%, #fff 8%) 0 4px;
        background: linear-gradient(top, #d9eaf3 0%, #fff 8%) 0 4px;
        -webkit-background-size: 100% 20px;
        -moz-background-size: 100% 20px;
        -ms-background-size: 100% 20px;
        -o-background-size: 100% 20px;
        background-size: 100% 20px;
        -webkit-border-radius: 3px;
        -moz-border-radius: 3px;
        border-radius: 3px;
        -webkit-box-shadow: 0 1px 2px rgba(0,0,0,0.07);
        -moz-box-shadow: 0 1px 2px rgba(0,0,0,0.07);
        box-shadow: 0 1px 2px rgba(0,0,0,0.07);
}
 
.paper::before {
        content: '';
        position: absolute;
        width: 4px;
        top: 0;
        left: 30px;
        bottom: 0;
        border: 1px solid;
        border-color: transparent #efe4e4;
}
 
textarea {
        display: block;
        width:94%;
        margin:0 auto;
        padding:3.8% 3%;
        border: none;
        outline: none;
        height: 94%;
        background: transparent;
        line-height: 20px;
}"><h1>Text Editor</h1>
</style>

<link rel="shortcut icon" href="http://g.etfv.co/https://docs.google.com"/>

<body OnLoad='document.body.focus();' contenteditable spellcheck="true" class="paper" >