- On Windows, use DPI set in print preview to set the printer DPI. Print
  preview DPI was previously only used for extension/cloud printers.
- Fix handling of non-square DPI - use x and y DPI to compute the
  correct page size to report from the printer instead of assuming
  both resolutions are the same when computing page size. Assuming both
  are identical results in incorrect page sizes for non square DPI.
- Note that we have to use only 1 DPI for rendering in both
  dimensions, this CL just fixes the bad page size behavior.

BUG=648774
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2795453002
Cr-Commit-Position: refs/heads/master@{#461799}