Fix AppCache unittests with NavigationLoaderOnUI enabled

The main changes are making these run on the UI thread instead of IO.
Also removes some references to net:: objects that aren't needed
anymore.

Bug: 824856
Change-Id: I99262c4dd1d364c7b5a03627121023bea5d671ca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1731298
Commit-Queue: Clark DuVall <cduvall@chromium.org>
Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683382}
4 files changed