[Tracing] Use TracingCategoryObserver in gc statistics

This patch is a follow-up patch to enable gc statistics to use
TracingCategoryObserver.

Previously we need to pass --track_gc_object_stats to v8 if we want to enable
gc statistics in tracing. In this patch, we introducce an integer flag
FLAG_gc_stats, and FLAG_track_gc_object_stats and FLAG_trace_gc_object_stats
will set it to 0x01, tracing will set it to 0x10 when we start tracing and
reset the bit when we stop tracing.

BUG=v8:5590

Review-Url: https://codereview.chromium.org/2459903003
Cr-Commit-Position: refs/heads/master@{#40817}
9 files changed
tree: ece04a530a7739d01db81e4ebfe2f48171b06fc6
  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. .gitignore
  16. .gn
  17. .ycm_extra_conf.py
  18. AUTHORS
  19. BUILD.gn
  20. ChangeLog
  21. CODE_OF_CONDUCT.md
  22. codereview.settings
  23. DEPS
  24. LICENSE
  25. LICENSE.fdlibm
  26. LICENSE.strongtalk
  27. LICENSE.v8
  28. LICENSE.valgrind
  29. Makefile
  30. Makefile.android
  31. OWNERS
  32. PRESUBMIT.py
  33. README.md
  34. snapshot_toolchain.gni
  35. 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.