Reland "[heap-profiler] Do not treat WeakMap values as weak."

This is a reland of c34042cc6441d7d3d600d3c1c6f7459c8ae7ad63
Original change's description:
> [heap-profiler] Do not treat WeakMap values as weak.
> 
> For the WeakHashTable objects only mark keys as weak while leaving values as strong references.
> 
> BUG=chomium:773722
> 
> Change-Id: Iabd5ba293d05fe68a2af6503fcdd711ecc182482
> Reviewed-on: https://chromium-review.googlesource.com/730771
> Commit-Queue: Alexei Filippov <alph@chromium.org>
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#48985}

TBR=ulan@chromium.org

Bug: chomium:773722
Change-Id: Icede16fde528d147cde5c3f6c72f2029876b099f
Reviewed-on: https://chromium-review.googlesource.com/740722
Reviewed-by: Alexei Filippov <alph@chromium.org>
Commit-Queue: Alexei Filippov <alph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48987}
3 files changed
tree: c44dedc9c52dade2090fef84ff2dd996eba1e655
  1. benchmarks/
  2. build_overrides/
  3. docs/
  4. gni/
  5. gypfiles/
  6. include/
  7. infra/
  8. samples/
  9. src/
  10. test/
  11. testing/
  12. third_party/
  13. tools/
  14. .clang-format
  15. .editorconfig
  16. .git-blame-ignore-revs
  17. .gitignore
  18. .gn
  19. .vpython
  20. .ycm_extra_conf.py
  21. AUTHORS
  22. BUILD.gn
  23. ChangeLog
  24. CODE_OF_CONDUCT.md
  25. codereview.settings
  26. DEPS
  27. LICENSE
  28. LICENSE.fdlibm
  29. LICENSE.strongtalk
  30. LICENSE.v8
  31. LICENSE.valgrind
  32. Makefile
  33. Makefile.android
  34. OWNERS
  35. PRESUBMIT.py
  36. README.md
  37. snapshot_toolchain.gni
  38. WATCHLISTS
README.md

V8 JavaScript Engine

V8 is Google's open source JavaScript engine.

V8 implements ECMAScript as specified in ECMA-262.

V8 is written in C++ and is used in Google Chrome, the open source browser from Google.

V8 can run standalone, or can be embedded into any C++ application.

V8 Project page: https://github.com/v8/v8/wiki

Getting the Code

Checkout depot tools, and run

    fetch v8

This will checkout V8 into the directory v8 and fetch all of its dependencies. To stay up to date, run

    git pull origin
    gclient sync

For fetching all branches, add the following into your remote configuration in .git/config:

    fetch = +refs/branch-heads/*:refs/remotes/branch-heads/*
    fetch = +refs/tags/*:refs/tags/*

Contributing

Please follow the instructions mentioned on the V8 wiki.