Revert of Sync GN unit tests with GYP, add checking script. (patchset #3 id:40001...

Revert of Sync GN unit tests with GYP, add checking script. (patchset #3 id:40001 of https://codereview.chromium.org/1289423004/ )

Reason for revert:
Breakage of tests on Linux GN. See crbug.com/521944 for more details.

Original issue's description:
> Sync GN unit tests with GYP, add checking script.
>
> Some of these JavaScript gtest tests were missing from the GN build because
> they needed to go into a special target.
>
> The included script will find and print out lists of test differences.
>
> Committed: https://crrev.com/b2f72715a4899c690f92529f91fa3a9adf9db5ff
> Cr-Commit-Position: refs/heads/master@{#343820}

TBR=jam@chromium.org,brettw@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=521944

Review URL: https://codereview.chromium.org/1284423005

Cr-Commit-Position: refs/heads/master@{#343886}