Setting "checked" attribute in shadow dom is removed on upgrade

[katlyn-edwards]

Description

Setting checked on a paper-checkbox with shadow dom enabled, is getting disabled on upgrade.
Looks like it's due to active not also being set in _buttonStateChanged of paper-checked-element-behavior.js

Expected outcome

Upgrading should maintain the state of the attributes

Actual outcome

Checked is reverted to false

Browsers Affected

• Chrome
• Firefox
  [didn't check anyone else]
• Safari 9
• Safari 8
• Safari 7
• Edge
• IE 11
• IE 10