[chrome:omnibox] Output table styling.

This CL intends to style the output table to approximately resemble the end goal. There will be more styling changes in future as 1) a single CL for all the styling changes would be too large, and 2) some of the styling changes depend on changes to how we generate and manage the HTML elements from the JS code.
In addition to 1) trivial CSS styling, this CL also 2) scales the table and column widths with the page width (down to a minimum width) and therefore gives all tables the equal width and consistent column widths; and 3) merges the combined results and individual provider results tables into a single table delimited with inner header rows.

Bug: 891303
Change-Id: Ifc823456a8404ade90f34a2c07545c1f643cb96d
Reviewed-on: https://chromium-review.googlesource.com/c/1354132
Commit-Queue: manuk hovanesian <manukh@chromium.org>
Reviewed-by: Tommy Li <tommycli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612335}
6 files changed