Delete unused WebCanonicalCookie::BuildCookieLine()

The BuildCookieLine() function violated layering by using
internal blink types in the blink public API but since it
wasn't used anyway it can just be deleted.

Also hide the export include from gn since it's an ugly
exception, just for debug component builds.

Bug: 800764

Change-Id: I7381e68f801e6037667d254d690faa376461e9da
Reviewed-on: https://chromium-review.googlesource.com/c/1301469
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Daniel Bratell <bratell@opera.com>
Cr-Commit-Position: refs/heads/master@{#603371}
3 files changed