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This patch migrates the helper libraries to avoid using the concept of
a 'seed', which was hard to grasp, and instead migrates tests to more
directly use keywords.

Change-Id: Ibcdae092baade651daca059850ac31f276f47564
Bug: None
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2495461Reviewed-by: Maksim Moskvitin <mmoskvitin@google.com>
Commit-Queue: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#821819}