DropDownMenu alignment issues in ToolBar

[huntwj]

(Could be related to #5839)

Problem description

When DropDownMenus are composed inside Toolbar components, they are not aligned with other text such as ToolbarTitle components.

<Toolbar>
  <ToolbarGroup>
    <ToolbarTitle text="Title Text" />
  </ToolbarGroup>
  <ToolbarGroup>
    <DropdownMenu>
      <MenuItem primaryText="First" value={1} />
      <MenuItem primaryText="Second" value={2} />
      <MenuItem primaryText="Third" value={3} />
      <MenuItem primaryText="Fourth" value={4} />
  </ToolbarGroup>
</Toolbar>

This is also visible on the Toolbar demo/documentation page: http://www.material-ui.com/#/components/toolbar

Versions

• Material-UI: 0.16.7
• React: 15.4.1
• Browser: Chrome 55.0.2883.95