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* Add ability to display additional text above the PaymentOption
  lists.

* Shipping address section now has the option to display text
  saying that the user needs to select a shipping address to
  update the shipping options.

* Optional shipping address section text disappears once the
  user selects an option.

BUG=603635

Review-Url: https://codereview.chromium.org/2040623002
Cr-Commit-Position: refs/heads/master@{#397900}