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 allows us to assert at compile time that a class instance is
assigned, which is particularly useful for Guard classes.

Change-Id: Id16b2bb70d29573566e821c908c1169d49ec57af
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2552415
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71397}

This is a reland of e95e1b62

After landing https://crrev.com/c/2546682, this CL can be relanded
without changes.

Original change's description:
> [heap] Introduce LocalIsolate for main thread
>
> Add a LocalIsolate for the main thread to Isolate. This LocalIsolate is
> kept alive during the whole lifetime of the Isolate. The main thread
> LocalIsolate starts in the Running state in contrast to the background
> thread LocalIsolates (those start in Parked).
>
> Code paths in Turbofan that used to create a LocalIsolate on the main
> thread can now simply use the main thread LocalIsolate.
>
> LocalIsolate for the main thread will help in reducing differences
> between the main and background threads. The goal is that the main
> thread behaves more like a background thread.
>
> The main thread LocalIsolate should also make it simpler to share code
> between main thread and background threads by using LocalIsolate for
> both.
>
> Bug: v8:10315
> Change-Id: I7fd61d305a6fd7079e2319d75c291c1021e70018
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2509593
> Reviewed-by: Simon Zünd <szuend@chromium.org>
> Reviewed-by: Yang Guo <yangguo@chromium.org>
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Reviewed-by: Leszek Swirski <leszeks@chromium.org>
> Reviewed-by: Georg Neis <neis@chromium.org>
> Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#71226}

Bug: v8:10315
Change-Id: I418b1217aeac4f3c44a0aa514dea9864f8a58656
TBR: szuend@chromium.org, yangguo@chromium.org, ulan@chromium.org, leszeks@chromium.org, neis@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2543399Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71274}

This reverts commit e95e1b62.

Reason for revert:
https://ci.chromium.org/p/v8/builders/ci/V8%20Linux%20-%20arm%20-%20sim%20-%20debug/23064

Original change's description:
> [heap] Introduce LocalIsolate for main thread
>
> Add a LocalIsolate for the main thread to Isolate. This LocalIsolate is
> kept alive during the whole lifetime of the Isolate. The main thread
> LocalIsolate starts in the Running state in contrast to the background
> thread LocalIsolates (those start in Parked).
>
> Code paths in Turbofan that used to create a LocalIsolate on the main
> thread can now simply use the main thread LocalIsolate.
>
> LocalIsolate for the main thread will help in reducing differences
> between the main and background threads. The goal is that the main
> thread behaves more like a background thread.
>
> The main thread LocalIsolate should also make it simpler to share code
> between main thread and background threads by using LocalIsolate for
> both.
>
> Bug: v8:10315
> Change-Id: I7fd61d305a6fd7079e2319d75c291c1021e70018
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2509593
> Reviewed-by: Simon Zünd <szuend@chromium.org>
> Reviewed-by: Yang Guo <yangguo@chromium.org>
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Reviewed-by: Leszek Swirski <leszeks@chromium.org>
> Reviewed-by: Georg Neis <neis@chromium.org>
> Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#71226}

TBR=ulan@chromium.org,yangguo@chromium.org,neis@chromium.org,leszeks@chromium.org,szuend@chromium.org,dinfuehr@chromium.org

Change-Id: Ia70b4bfe3b8fa26bf8d6a7dc612a310b0ed54073
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:10315
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2543937Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71228}

Add a LocalIsolate for the main thread to Isolate. This LocalIsolate is
kept alive during the whole lifetime of the Isolate. The main thread
LocalIsolate starts in the Running state in contrast to the background
thread LocalIsolates (those start in Parked).

Code paths in Turbofan that used to create a LocalIsolate on the main
thread can now simply use the main thread LocalIsolate.

LocalIsolate for the main thread will help in reducing differences
between the main and background threads. The goal is that the main
thread behaves more like a background thread.

The main thread LocalIsolate should also make it simpler to share code
between main thread and background threads by using LocalIsolate for
both.

Bug: v8:10315
Change-Id: I7fd61d305a6fd7079e2319d75c291c1021e70018
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2509593Reviewed-by: Simon Zünd <szuend@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71226}