To indicate that the Isolate* in getters might not be a "real" isolate,
but rather a calculated one from GetIsolateForPtrCompr only used for
calculating the isolate root, make that function return a const Isolate*
and change field getters, Object::IsFoo predicates, and related
functions to all take a const Isolate* instead of an Isolate*

With this change, we can slightly more confidently use Objects that are
in OffThreadSpace, without having to worry too much about having an
Isolate* floating around that could accidentally be used.

This is a slight abuse of const semantics, but it allows implicit
conversion from Isolate* arguments to the const Isolate* parameter.

Bug: v8:7703
Bug: chromium:1011762
Change-Id: I54d4a65d2299477195f4d754cabe64ce34fdaa4c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1939455
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65199}

This CL adds build flags for pluging in third-party heap implementation.
Additionally it redirects allocation requests when the flags are on.

Bug: v8:9533

Change-Id: I7ef300ca9dc2b5f498a13211611ae4b4b3df8fa0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1928860
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65114}

... in addition to existing [Heap]Object::IsXXX().

The idea is to use these getters in hot C++ code since passing isolate
explicitly makes it trivial to compute isolate root value and reduces
the C++ code size.

For full-pointer mode the unused isolate argument will be optimized
away by the compiler, so full-pointer mode should not be affected
in any sense.

Bug: v8:9353
Change-Id: I405cd54e8895b58f60f797fdb1c1b5654acb56f3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1664337
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62335}

Bug: v8:9183
Change-Id: Ib17445fe22da683c5be4c3f0249a31502040c2dd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1672935Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62331}