Dropdown hidden when in a RIGHT-DRAWER drawer panel which is expanded

[yorrd]

Description

The dropdown menu choices box is not visible in an expanded right-drawer.

Steps to reproduce

1. create a paper-drawer-panel
2. put a dropdown menu within the drawer
3. use th eattribute left-drawer for the drawer panel
4. make the window small enough so that the drawer disappears
5. expand the drawer
6. try to use the dropdown

   Browsers Affected

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