Allows embedders to allocate C++ objects on the internal managed C++
heap.

Bug: chromium:1056170
Change-Id: Ibd81d0fc915478a81f14e8ab12a631e442790f04
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2536642Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71225}

This CL adds TraceWeakContainer and VisitWeakContainer to the Visitor
api. It also introduces the weak_container_worklist_ used to force
re-tracing of weak containers that are reachable from stack.

Bug: chromium:1056170
Change-Id: I4ba75bd64939b8df9ece7422828a5ac647b03fd1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2491022
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70708}

Bug: chromium:1056170
Change-Id: Ib03a09db010f3ad06701520fc39e7e83055dbb9e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2467855
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Auto-Submit: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70515}

This is a revival of https://chromium-review.googlesource.com/c/v8/v8/+/2228332

The CL establishes the following:
*) Objects are marked before being pushed to the worklists.
*) Live bytes are always accounted after tracing an object (i.e. move
   from Gray to Black below).
*) Previously not fully constructed objects are traced immediately
   instead of pushed to the marking worklist.

This establishes the following invariants for all marking worklists:
1) White = !object.is_marked() && !worklist.contains(object)
2) Gray = object.is_marked() && worklist.contains(object)
3) Black = object.is_marked() && !worklist.contains(object)

Bug: chromium:1056170
Change-Id: I821573b3fbc057e6ffb836154271ff986ecb4d2b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2336797Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69268}

- Adds JSVisitor that is used for unified heap marking.
- Adds JSMember as supported reference type that also encapsulates a
  write barrier in future. JSMember is a replacement for
  TracedReference which can be deprecated with EmbedderHeapTracer once
  the library is used to handle unified heap collections.

The dispatch for v8::JSMember on cppgc::Visitor is provided through a
specialization of TraceTrait.

Bug: chromium:1056170
Change-Id: I60d976ae66db3e5fa2e690a21627bdcb8c6871af
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2284488Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68716}

Split off ConservativeMarkingVisitor from MarkingVisitor.

After this change, MarkingVisitor and ConservativeMarkingVisitor are
types that are instantiated with Marking and merely forward to
MarkingState accrodingly. The two marking-related visitors can be
passed along as interface types cppgc::Visitor and
ConservativeTracingVisitor, respectively.

Change-Id: Iad103dc3053c61d1a104a8802edd420d21cdf935
Bug: chromium:1056170
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2270538
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68661}

- Untangles MarkingVisitor from Marker.
- Adds ConservativeTracingVisitor encapsulating conservative
  tracing.

This enables the following architecture:
- Marking visitors (unified + stand-alone) inherit from
  MarkingVisitor;
- Markers (unified + stand-alone) inherit (or directly use) Marker

Bug: chromium:1056170
Change-Id: I05304c231d2983dab5611d05cf4aa8bfa3ed5e20
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2245600Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68366}

Document:
- Visitor

Bug: chromium:1056170
Change-Id: Icc0037befa73f043fcbf14ff4ff89be8b8940ee4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2235696Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68233}

Provides the infrastructure to register weak callbacks for
WeakMember<T> through visitor. The WeakCallbackInfo broker is used to
query objects for liveness. In a future CL the same broker object is
passed to custom weak callbacks.

Change-Id: I8b5a66354e0e457521989d40ae64a9558c339503
Bug: chromium:1056170
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2142265
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67109}

This CL adds the necessary traits to dispatch from Member through a
visitor implementation for GarabgeCollected and GarbageCollectedMixin.

Bug: chromium:1056170
Change-Id: I12680335044aaa842639fb5e8f9a3ac61587f51a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2138431Reviewed-by: Hannes Payer <hpayer@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67041}