This adds inference for general JSObjects to NativeContextInferrer in
the case when the object is going to be attributed to the shard context.

Bug: chromium:973627
Change-Id: I393e8dd16a1f8b615fb2f8dceb52f543bae33554
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1997133Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65736}

This changes the marking worklist draining for the main thread
marker and the concurrent marker to use the following algorithm in
per-context mode:
1) Pop an object from the marking worklist.
2) Try to infer the native context that owns the objects.
   This is done using a new NativeContextInferrer class.
3) If the inference is successful, then change the active marking
   worklist to the worklist of the inferred native context.
4) Otherwise, keep the current active marking worklist.
5) Visit the object. Newly discovered objects will be pushed
   onto the active marking worklist.
6) Account the object size for the native context corresponding
   to the active marking worklist.
   This is done using a new NativeContextStats class.

The main property of the algorithm is that each object for which
we couldn't infer the native context is either attributed to
the native context retaining it or is not attributed to any native
context.

Bug: chromium:973627

Change-Id: Ide4ab992275d115279f971d89ace657f4c05e176
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1981491
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65663}

This adds a new API function and provides a simple implementation
of performance.measureMemory() in d8. The implementation currently
immediately resolves the result promise with the current heap size.

Bug: chromium:973627

Change-Id: Ia8e1963a49b7df628b5487a2c0d601473f0cb039
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1796502
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63694}