Print Preview: Make Scaling settings a dropdown

Makes scaling settings a dropdown with 3 options: Default, Custom, and
Fit to Page. Fit to Page option is only available for PDFs. Selecting
the custom option displays the current number input for scaling.

Bug: 930008
Change-Id: I77b3c356f0592f360c87f8d4c58fe5322719208d
Reviewed-by: Demetrios Papadopoulos <>
Commit-Queue: Rebekah Potter <>
Cr-Commit-Position: refs/heads/master@{#631491}
12 files changed