Add document type into print parameter

Add document type into print parameter so that the renderer may return
printed document in different formats such as PDF, or Skia multi-picture
types. This is to prepare renderers to send back printed result in Skia
multi-picture format to be composed later.

BUG=455764

Change-Id: I2423ba4b35cc4c26ad43050988efc8d6107c6565
Reviewed-on: https://chromium-review.googlesource.com/627583
Commit-Queue: Wei Li <weili@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#497485}
9 files changed