Revert of DevTools: simplify JSONValues API, prepare to the OwnPtr migration. (patchset #2 id:20001 of https://codereview.chromium.org/1728873002/ )

Reason for revert:
Collided with https://codereview.chromium.org/1730653002

Original issue's description:
> DevTools: simplify JSONValues API, prepare to the OwnPtr migration.
>
> Committed: https://crrev.com/43c8de64e250e814ea15c4240d5d4273a8272535
> Cr-Commit-Position: refs/heads/master@{#377409}

TBR=dgozman@chromium.org,pfeldman@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/1734693003

Cr-Original-Commit-Position: refs/heads/master@{#377411}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 74b1089154339a81247f7d21630b7abc98980d13
2 files changed