So far the main thread can have two different kinds of local handles,
regular main thread handles and local handles in its LocalIsolate. This
is both confusing and error-prone.

This CL retargets local handles creation for the LocalIsolate on the
main thread to always create regular main thread handles instead.

Bug: v8:10315
Change-Id: I4df509a0fc1bd630ba956b5eaacacbe706ddb4ef
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2527062Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71534}

Bug: v8:11074
Change-Id: I7af4fb1fd93e1b369fdca5b9e726dcafa43b0afb
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2565081Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71476}

Scopes in V8 are used to guarantee one or more properties during its
lifetimes. If a scope is not named e.g MyClassScope(args) instead of
MyClassScope scope(args) it will get created and automatically destroyed
and therefore, being useless as a scope. This CL would produce a
compiling warning when that happens to ward off this developer error.

Follow-up to ccrev.com/2552415 in which it was introduced and
implemented for Guard classes.

Change-Id: Ifa0fb89cc3d9bdcdee0fd8150a2618af5ef45cbf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2555001
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71425}

This patch introduces a new LocalIsolate and LocalFactory, which use
LocalHeap and replace OffThreadIsolate and OffThreadFactory. This allows
us to remove those classes, as well as the related OffThreadSpace,
OffThreadLargeObjectSpace, OffThreadHeap, and OffThreadTransferHandle.
OffThreadLogger becomes LocalLogger.

LocalHeap behaves more like Heap than OffThreadHeap did, so this allows
us to additionally remove the concept of "Finish" and "Publish" that the
OffThreadIsolate had, and allows us to internalize strings directly with
the newly-concurrent string table (where the implementation can now move
to FactoryBase).

This patch also removes the off-thread support from the deserializer
entirely, as well as removing the LocalIsolateWrapper which allowed
run-time distinction between Isolate and OffThreadIsolate. LocalHeap
doesn't support the reservation model used by the deserializer, and we
will likely move the deserializer to use LocalIsolate unconditionally
once we figure out the details of how to do this.

Bug: chromium:1011762

Change-Id: I1a1a0a72952b19a8a4c167c11a863c153a1252fc
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2315990
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69397}

Zap freed local and persistent handles similar to main thread handles.
As a drive-by change, fix the creation of local handles without
LocalHandleScope.

Bug: v8:10315
Change-Id: Ia71bc5419c62ae073928751f57fc221ea11de254
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2323362
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69121}

This CL allows LocalHandles to be dereferenced by the same thread that
created them, even if we have a DisallowHandleDereference scope.

Bug: v8:7790
Change-Id: Ie227aaa4152c887d0d9c913dfa35217166726614
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2316111Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69068}

Add LocalHandleScope to allow for local handles in LocalHeaps
(background threads). This class is similar to HandleScope which still
needs to be used on the main thread. When performing a GC, the main
thread halts all background threads at a safepoint such that it can
safely iterate their roots.

Bug: v8:10315
Change-Id: Id8f5d54cc2535e004081ccdef15dc03a39b2d0f0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2111218
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66853}