Dom-if by user role with polymer & firebase using firebase-auth and google as provider

I am trying to show a dom-if template only to some users, but I don't know how to do it. Here is a pseudocode of what I am trying to do:

 <template is="dom-if" if="{{user.isAdmin}}" restamp="true">
        <hr />
        <h1>Add new conference:</h1>
        <paper-input
        id="title"
        label="Título"
        type="text"
        name="title">
    </paper-input>
    <paper-fab id="saveFab" icon="cloud-upload" on-tap="add"></paper-fab>
</template>
<script>
        Polymer({
            is: 'my-conferences',
            properties: {
                data: Array,
                user: Object,
            },

...

Where "user" is the object that I got from the <firebase-auth> element. Something like user.isAdmin is what I would like to achieve.

Any ideas? Thank you!

here is a way you could do this.

1. Create a users record on you firebase with the same id.

then:

    <firebase-auth id="auth" provider="google" user="{{auth}}" on-error="showError">
</firebase-auth>

<app-user
    uid="[[auth.uid]]"
    user="{{user}}"></app-user>

App user element is

<script>
    (function() {
        'use strict';
        Polymer({
            is: 'app-user',

            properties: {
                uid: {
                    type: String,
                    reflectToAttribute: true,
                    notify: true,
                    observer: '_uidChanged'
                },
                user: {
                    type: Object,
                    value: null,
                    notify: true
                }
            },

            _uidChanged: function (uid) {

                if (this.uid) {
                    firebase.database().ref('/users/' + uid).once('value', function(snapshot) {
                        if (snapshot.val()) {
                            this.user = snapshot.val();
                        }
                    }.bind(this));

                }
            }
        });
    })();
</script>

let me know if you need more help.