WebUI dark mode: Make cr-input background consistent with md-selects

- Make cr-input's background color consistent with md-select
- Fix the background of the search icon in Print Preview's search box
cr-input, so that it is the same color as the rest of the input.

Bug: 954416
Change-Id: Iecc5c342ef6bd7f9e0400642ab6bab117164a79a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1575029
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Reviewed-by: Dan Beam <dbeam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#652464}
2 files changed