Polymer 1.0 paper-menu-button horizo​​ntalAlign和horizo​​ntalOffset不工作

Question

我有以下代码：

<paper-toolbar id="mainToolbar">
    <paper-icon-button id="paperToggle" icon="menu" paper-drawer-toggle></paper-icon-button>
    <div class="app-name">Dashbord</div>
    <span class="flex"></span>
    <paper-menu-button horizontalAlign="right" horizontalOffset="20" verticalAlign="top" verticalOffset="50">
        <paper-icon-button icon="more-vert" class="dropdown-trigger"></paper-icon-button>
        <paper-menu class="dropdown-content">
            <paper-item>Share</paper-item>
            <paper-item>Settings</paper-item>
            <paper-item>Help</paper-item>
        </paper-menu>
   </paper-menu-button>
</paper-toolbar>

菜单按钮按预期工作，但下拉horizontalAlign和horizontalOffset属性不会生效。

我让下拉菜单工作的唯一方法是对元素定义中的值进行硬编码：

<iron-dropdown
  id="dropdown"
  opened="{{opened}}"
  horizontal-align="right"
  vertical-align="top"
  horizontal-offset="50"
  vertical-offset="20"
  open-animation-config="[[openAnimationConfig]]"
  close-animation-config="[[closeAnimationConfig]]"
  no-animations="[[noAnimations]]"
  focus-target="[[_dropdownContent]]">
  <paper-material class="dropdown-content">
    <content id="content" select=".dropdown-content"></content>
  </paper-material>
</iron-dropdown>