Fix webview crash where PathUtils is not initialized in time

Moves initialization into ChromeApplication so that it will always
happen in time. This was a regression introduced by a4c2023.

TBR=agrieve  # trivial refactor to a couple tests

Bug: 978328
Change-Id: Iaf7c99b4d0c3e11f0419e076a5430f9a3cd48cda
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1677729
Reviewed-by: Richard Coles <torne@chromium.org>
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#672634}
22 files changed