Revert of Removed support deprecated (//@|/*@) source(URL|MappingURL)= (patchset #1 id:1 of https://codereview.chromium.org/1474543005/ )

Reason for revert:
Failing layout tests:

inspector/tracing/timeline-event-causes.html
virtual/syncpaint/inspector/tracing/timeline-event-causes.html
inspector/animation/animation-timeline-fill.html
virtual/threaded/inspector/tracing/timeline-event-causes.html
inspector/tracing/timeline-script-id.html
inspector/sources/debugger-ui/source-url-comment.html
inspector/console/console-log-linkify-stack-in-errors.html
virtual/syncpaint/inspector/tracing/timeline-script-id.html
virtual/threaded/inspector/tracing/timeline-script-id.html

Original issue's description:
> Removed support deprecated (//@|/*@) source(URL|MappingURL)=
>
> LOG=Y
> BUG=chromium:558998
> R=yangguo@chromium.org
>
> Committed: https://crrev.com/c1e5f005d79c436d90f474f8bc6448c4555a619f
> Cr-Commit-Position: refs/heads/master@{#32249}

TBR=machenbach@chromium.org,kozyatinskiy@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:558998

Review URL: https://codereview.chromium.org/1481513002

Cr-Commit-Position: refs/heads/master@{#32259}