Start storing locations in heap snapshot file. Initial support
for closure, additional object types might be added in the future.
Needed to show source code locations for objects in the DevTools
heap snapshot viewer.

Bug: chromium:854097
Change-Id: I12659373ce1adf67b55c6a10ea1d0465fcdb4a10
Reviewed-on: https://chromium-review.googlesource.com/1174257
Commit-Queue: Dominik Inführ <dinfuehr@google.com>
Reviewed-by: Alexei Filippov <alph@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55245}