Introduce StartupData in /content/public/browser, and
StartupDataImpl in /content/browser.
This is a precursor CL for: https://crrev.com/c/1108178. In the
follow up CL, StartupData* will be plumbed via
MainFunctionParams to create the browser main loop.
Bug: 846846, 853308
Change-Id: Ic192cfa696439996dec07435f1980d78282f15db
Reviewed-on: https://chromium-review.googlesource.com/1117471
Commit-Queue: Xi Han <hanxi@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#573943}
