Arrow key operations for number type not working in IE11

[diregraph]

Description

Arrow keys does not work (to increment/decrement number type) for iron-input in IE11

Expected outcome

When a number type iron-input is selected user should be able to increment/decrement with arrow keys

Actual outcome

When a number type iron-input is selected user is not able to increment/decrement with arrow keys

Live Demo

N/A, need to transpile to ES5

Steps to reproduce

1. Put a number type iron-input element in the page.
2. Build with polymer build
3. Serve with prpl-server --root ./build
4. Open in IE11
5. Tab navigate or click on the element and try increment/decrement with arrow keys

Browsers Affected

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