Split PrefetchBrowserTest

Bug: 935267
Change-Id: Id1f322e440458726691a860a5512606132ba9c24
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1580991
Commit-Queue: Tsuyoshi Horo <horo@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Kunihiko Sakamoto <ksakamoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#657101}
5 files changed