To enable the HTML in list view you need to override the method _format() as below.(for Odoo v10)

**JS**

    odoo.define('html_in_tree_field.web_ext', function (require) {

        "use strict";

     var Listview = require('web.ListView');

     var formats = require('web.formats');

     Listview.Column.include({

         _format: function (row_data, options) {

      // Removed _.escape() function to display html content.

      // Before : return _.escape(formats.format_value(row_data[this.id].value, this, options.value_if_empty));

      return formats.format_value(row_data[this.id].value, this, options.value_if_empty);

         }

     });

    });

**XML to add above JS.**

    <?xml version="1.0" encoding="utf-8"?>

    <odoo>

     <template id="assets_ext" inherit_id="web.assets_backend">

       <xpath expr="." position="inside">

           <script type="text/javascript" src="/html_in_tree_field/static/src/js/web_ext.js"></script>

       </xpath>

     </template>

    </odoo>

**__manifest__.py**

    {

    ...

    ...

    'data': [

            ...

            'views/above_xml_filename.xml',

        ],

    ....

    }