The overall goal is to modernize the UI codbase of PP by leveraging Web Components (with Polymer), while keeping the UI looking the same initially. This will enable us to later perform a UI refresh with less work, compared to trying to do it all at once (Componetize+UI refresh).
Some initial scaffolding work needs to be done to kick-start this effort.
1) Add a enable-new-print-preview runtime flag
2) Decide exactly where the new PP code will leave, and how it can leverage existing JS files
Proposal: chrome/browser/resources/print_preview/new/
Putting the code under the existing folder will allow for easier re-using files as necessary from the existing PP UI.
3) Hook up the flag to trigger print preview with a dummy empty page for now.