2.1.0 breaks existing scrolling listeners on firefox

[giona69]

Description

I register a scrolling listener on the main app
I click on iron-dropdown powered element (ex: paper-menu-button)
main listener do not receive events any more

Expected outcome

main listener will continue receiving events

Actual outcome

main listener do not receive events any more

Steps to reproduce

start polymer starter kit
in the ready method register the event listener:

                    this.scrollTarget = this.$.layout.shadowRoot.querySelector('#contentContainer');

                    this.scrollTarget.addEventListener('scroll', () => {
                        this.scrollPos = this.scrollTarget.scrollTop;

                        if ((this.scrollTarget.scrollHeight - this.scrollPos - this.scrollTarget.offsetHeight) < 400) {
                            Utils.log('MAIN', 'FIRE! ' + this.fireThreshold);
                            this.fireThreshold = true;
                        }
                    });

place a paper-menu-button wherever you want

                    <paper-menu-button id="menul" horizontal-align="right">
                        <paper-fab mini id="langfab" slot="dropdown-trigger" src="[[pngUrl]]" on-click="flagClick"></paper-fab>
                        <paper-listbox slot="dropdown-content" selected="{{menulanguage}}" class="listmenu">
                            <paper-icon-item class="filteritem">
                                <iron-icon src="images/it.png" class="flagicon" slot="item-icon"></iron-icon>
                                <span>[[locale.italian]]</span>
                            </paper-icon-item>
                            <paper-icon-item class="filteritem">
                                <iron-icon src="images/en.png" class="flagicon" slot="item-icon"></iron-icon>
                                <span>[[locale.english]]</span>
                            </paper-icon-item>
                            <paper-icon-item class="filteritem">
                                <iron-icon src="images/es.png" class="flagicon" slot="item-icon"></iron-icon>
                                <span>[[locale.spanish]]</span>
                            </paper-icon-item>
                            <paper-icon-item class="filteritem">
                                <iron-icon src="images/br.png" class="flagicon" slot="item-icon"></iron-icon>
                                <span>[[locale.brazilian]]</span>
                            </paper-icon-item>
                            <paper-icon-item class="filteritem">
                                <iron-icon src="images/ru.png" class="flagicon" slot="item-icon"></iron-icon>
                                <span>[[locale.russian]]</span>
                            </paper-icon-item>
                            <paper-icon-item class="filteritem">
                                <iron-icon src="images/uk.png" class="flagicon" slot="item-icon"></iron-icon>
                                <span>[[locale.ukrainian]]</span>
                            </paper-icon-item>
                            <paper-icon-item class="filteritem">
                                <iron-icon src="images/ro.png" class="flagicon" slot="item-icon"></iron-icon>
                                <span>[[locale.romanian]]</span>
                            </paper-icon-item>
                            <paper-icon-item class="filteritem">
                                <iron-icon src="images/cu.png" class="flagicon" slot="item-icon"></iron-icon>
                                <span>[[locale.cuban]]</span>
                            </paper-icon-item>
                            <paper-icon-item class="filteritem">
                                <iron-icon src="images/ve.png" class="flagicon" slot="item-icon"></iron-icon>
                                <span>[[locale.venezuelan]]</span>
                            </paper-icon-item>
                            <paper-icon-item class="filteritem">
                                <iron-icon src="images/do.png" class="flagicon" slot="item-icon"></iron-icon>
                                <span>[[locale.dominican]]</span>
                            </paper-icon-item>
                            <paper-icon-item class="filteritem">
                                <iron-icon src="images/pt.png" class="flagicon" slot="item-icon"></iron-icon>
                                <span>[[locale.portoguese]]</span>
                            </paper-icon-item>
                            <paper-icon-item class="filteritem">
                                <iron-icon src="images/fr.png" class="flagicon" slot="item-icon"></iron-icon>
                                <span>[[locale.french]]</span>
                            </paper-icon-item>
                            <paper-icon-item class="filteritem">
                                <iron-icon src="images/de.png" class="flagicon" slot="item-icon"></iron-icon>
                                <span>[[locale.german]]</span>
                            </paper-icon-item>
                        </paper-listbox>
                    </paper-menu-button>

start the application locally with polymer serve

start scrolling
click on the paper-menu-button
start scrolling again
verify scrolling doesn't fire anymore on the main event
only in FIREFOX

for a workaround I reverted to 2.0.0

Browsers Affected

• Chrome
• [x ] Firefox
• Safari 9
• Safari 8
• Safari 7
• Edge
• IE 11
• IE 10

[mvtorres]

Thanks, the workaround fixed the issue for me.

This issue also affects Edge.