Fix no-state prefetch handling with KeepAliveRenderer feature

A browser test for no-state prefetch failed for
KeepAliveRendererForKeepaliveRequests feature, which meant a bug. This
CL fixed the mishandling. With this CL, "keepalive" flag is
transferred from the renderer to the browser, and the feature affects
only requests with "keepalive" flag.

The non-state prefetch browser tests are now run in both settings
(i.e., with/without the feature).

Bug: 695939
Change-Id: I77c42cce95346f034af3ef4b7496908affc3074d
Reviewed-on: https://chromium-review.googlesource.com/656741
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501181}
10 files changed