... in regexp bytecode {length,name} accessors and in peephole
optimization.

Bug: chromium:1095866
Change-Id: I78c89d35d796776b61eabf82b921f7582e431be7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2250243Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68400}

The {NextInstruction} method is quite hot, since it's called for every
since Wasm instruction. It currently does several checks to figure out
if
- a breakpoint needs to be emitted,
- extra source positions are needed, or
- tracing is active.

The first two can only happen if we are generating debug code, hence
check for that first. The last can only happen in debug mode, so it's
not an issue in production.

Finally, outline the emission of debug information. This leads to
inlining of the {NextInstruction} method into callers, where it is a
single check followed by a call to {EmitDebuggingInfo} (in release
mode).

R=thibaudm@chromium.org

Bug: v8:10576
Change-Id: I5047406f55cd14c6c639528ef6e3422af27d16b1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2249671
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68399}

https://github.com/tc39/ecma262/pull/1776 is a normative change that
reached consensus in the November 2019 TC39. It changes
%AsyncFromSyncIteratorPrototype% methods to forward the absence of
arguments to the underlying sync iterator. This is observable via
`arguments.length` inside the underlying sync iterator.

For example, .next is changed to, roughly:

```
%AsyncFromSyncIteratorPrototype%.next = function(value) {
  let res;
  if (arguments.length < 1) {
     res = [[SyncIteratorRecord]].[[Iterator]].next();
  } else {
     res = [[SyncIteratorRecord]].[[Iterator]].next(value);
  }
  // ...
};
```

Bug: v8:10395
Change-Id: Ib8127d08cd78b8d502e6510241f3f13fbbaba5c7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2247041Reviewed-by: Marja Hölttä <marja@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68398}

... because tools/v8heapconst.py was created for default x64 release
mode (with enabled pointer compression).

Bug: v8:7703, v8:10621
Change-Id: I1fbcd81aac26e0b357279b7dffa97c64a5415e40
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2250238Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68397}

This reverts commit e0c1a349.

Reason for revert: Fails on Linux 64 cfi https://ci.chromium.org/p/v8/builders/ci/V8%20Linux64%20-%20cfi/25283?

TBR=omerkatz@chromium.org,mlippautz@chromium.org,bikineev@chromium.org,bikineev@chromium.org

Change-Id: I2b208c4019979735925bff5e0551291fae6a14d6
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2250320Reviewed-by: Zhi An Ng <zhin@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68396}

If mksnapshot fails then all that is printed is
    "FAILED: gen/v8/embedded.S snapshot_blob.bin"
and the command line. That complicates the investigation. Printing the
error code in run.py can help. The printing code handles large negative
numbers specially so that special Windows failure codes like 0xC0000005
are recognizable.

This code was tested by adding this early-out to main in mksnapshot.cc.

  if (argc < 1000)
    return 0xc0000005;

Bug: Chromium:1095767
Change-Id: I5dc81d368beaa339f0c519ce1c01bd13cdb18d93
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2249518
Auto-Submit: Bruce Dawson <brucedawson@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68395}

The CL addresses two issues with (Weak)Persistent and WeakMember:
1. (Weak)Persistent pointers are cleared on heap teardown. Before this
   CL the pointers would contain stale values which could lead to UAF.
2. WeakPersistent and WeakMember are cleared using a combination of
   internal clearing methods and mutable fields which avoids the use
   of const_cast<>.

Bug: chromium:1056170
Change-Id: Ibf2b0f0856771b4f6906608cde13a6d43ebf81f3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2248190Reviewed-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@{#68394}

Clenaups:
 * Encapsulated same code in methods
 * Inlined trace prints
 * Don't set as queued, we are going to visit it anyway
 * Moved the phi check updwards

Bug: v8:10424
Change-Id: I82534399617d97d717c5c0dd1ca4bfef9df91e97
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2218037
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68393}

Inline TransferStackSlot and compare the slots first. This is redundant
if they are different, but in most cases they are the same and doing
this check is beneficial.
Other methods of StackTransferRecipe are not called as often, and
inlining them seems negligible.

R=clemensb@chromium.org

Bug: v8:10576
Change-Id: Ibdaa714e3e40c95a79a0da3ca3170d1da7b62cf3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2249677
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68392}

Change-Id: I9a91bd41bc4429509457d73c78fc88e2cf826fb6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2248202Reviewed-by: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Milad Farazmand <miladfar@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#68391}

Since ReadOnlySpace pages will soon not be MemoryChunks, change most
uses of MemoryChunk::FromHeapObject and FromAddress to use the
BasicMemoryChunk variants and which use the new MemoryChunk::cast
function that takes a BasicMemoryChunk and DCHECKs !InReadOnlySpace().

To enable this, it also moves into BasicMemoryChunk several MemoryChunk
functions that just require a BasicMemoryChunk.

Bug: v8:10454
Change-Id: I80875b2c2446937ac2c2bc9287d36e71cc050c38
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2243216
Commit-Queue: Dan Elphick <delphick@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68390}

According to the spec, the section name does not start with a dot:
https://yurydelendik.github.io/webassembly-dwarf/#external-DWARF

Change-Id: I4ac205332dd9612fe83c2e6322a98bdae3ffa79d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2249669Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Philip Pfaffe <pfaffe@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68389}

The SafeStackFrameIterator, used in the profiler, sometimes uses the
link register instead of a return address stored on the stack, to get
more accurate results. This happens in particular for bytecode handlers
that do not create a stack frame. Authentication of PC for those frames
would fail in the SafeStackFrameIterator, as the "PC address" would not
point to a stack location with a signed return address, but instead to
a member of the SafeStackFrameIterator class where the value of the link
register was stored. We address this by skipping authentication of PCs
in the profiler.

Bug: v8:10026
Change-Id: I331c6c68e703db766be1891efffa69c2f9794e8a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2242954Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Georgia Kouveli <georgia.kouveli@arm.com>
Cr-Commit-Position: refs/heads/master@{#68388}

This is a reland of 539f0ed2

The reland fixes creating TimeDelta from double which requires
saturated_cast<>. Improvements to this constructions are tracked
in v8:10620.

Original change's description:
> cppgc,heap: Implement atomic unified heap GC
>
> Add v8::CppHeap as an implementation of a cppgc heap that
> integrates with V8's existing EmbedderHeapTracer API. The
> current implementation only supports non-incremental marking.
>
> Bug: chromium:1056170
> Change-Id: I4a09eb5ae57f5c7defe35eb3fe346627eb492473
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2245610
> Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
> Reviewed-by: Anton Bikineev <bikineev@chromium.org>
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Reviewed-by: Omer Katz <omerkatz@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#68374}

Bug: chromium:1056170,v8:10620
Change-Id: I39e15790e5cafe24da2a14d0bae6543391ebb536
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2248191Reviewed-by: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68387}

This fixes a check in the code that recompiles Liftoff
if breakpoints were removed on isolate removal.

Change-Id: I969b1b027a393f48e92ef4df37f6e672d16866cc
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2247648Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Kim-Anh Tran <kimanh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68386}

{std::ostream} was used without including either <ostream> or <iosfwd>.

R=ahaas@chromium.org

Change-Id: I92facf672c81a17e2ff24658bbefd961b4f4d445
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2248196Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68385}

This fixes a bug when an encoded character appears in the difference
string. Python3 doesn't require any encoding.

TBR=tmrts@chromium.org

No-Try: true
Bug: chromium:1095964
Change-Id: I49c66b5b9c105ad64d3a7839d0eb5df97ff5f404
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2249660Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68384}

- rename to ReplaceWithBuiltinCall (stubs are no longer a thing).
- add a convenience override that takes only the node and builtin id.

Bug: v8:8888
Change-Id: I7e19c3676c19c3f1b7c7f9a0cbbc3306fef8fc47
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2247651
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68383}

Bug: v8:8888
Change-Id: I0492385023fe01f1aacbd5eae9bb5930a5484062
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2247649
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68382}

... for nci code, in which several phases of the compiler are not
active:

LowerJSCreateCatchContext
LowerJSCreateEmptyLiteralObject
LowerJSCreateIterResultObject
LowerJSCreateWithContext
LowerJSGetIterator
LowerJSGetTemplateObject

With this change, the nci variant passes the test suite. Tests
relying on turbofan-specific behavior (e.g. deopts) are skipped.

Bug: v8:8888
Change-Id: I709178241e9b25e7480a39b4fb64bdcf576483be
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2245604
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68381}

The Isolate::context field doesn't track the context while JS is
executing. It's updated at boundary sites when entering runtime
through CEntry or returning to runtime in Invoke(). These set_context
calls are unnecessary.

Bug: v8:8888
Change-Id: Ifb9818b47699d2b1b37ebf0c19c2caf59fd17427
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2247772
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68380}

This adds the following things:
- age table for 4K regions;
- generational barrier for mixed 4K regions;
- unmarking for major collections;
- young generation flags.

Bug: chromium:1029379
Change-Id: Ief1229f0dac5f90c5f06d3168c8ffb4b7d1f1b53
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2246566
Commit-Queue: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68379}

Rolling v8/build: https://chromium.googlesource.com/chromium/src/build/+log/a980f85..78f36d4

Rolling v8/third_party/catapult: https://chromium.googlesource.com/catapult/+log/9253b25..fbbd9ca

Rolling v8/third_party/depot_tools: https://chromium.googlesource.com/chromium/tools/depot_tools/+log/e364dd8..3eb899a

TBR=machenbach@chromium.org,tmrts@chromium.org,v8-waterfall-sheriff@grotations.appspotmail.com

Change-Id: I4087b7a65d3cb180f9eaf0670463c221733e4f2e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2249338Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Commit-Queue: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#68378}

Change-Id: I69379880ef201f3668f54e8e3594c3933b5a6947
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2247758
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68377}

R=ecmziegler@chromium.org

Bug: v8:10556
Change-Id: Id105f2e5fa605e31ae6841062192edde10a94767
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2247650Reviewed-by: Emanuel Ziegler <ecmziegler@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68376}

This reverts commit 539f0ed2.

Reason for revert: UBSan failures https://ci.chromium.org/p/v8/builders/ci/V8%20Linux64%20UBSan/11626?

TBR=ulan@chromium.org,mlippautz@chromium.org,bikineev@chromium.org,bikineev@chromium.org

Change-Id: I9a8c88bd5a81a55795fba077056ad1ef37287186
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2248780
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Reviewed-by: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68375}

Add v8::CppHeap as an implementation of a cppgc heap that
integrates with V8's existing EmbedderHeapTracer API. The
current implementation only supports non-incremental marking.

Bug: chromium:1056170
Change-Id: I4a09eb5ae57f5c7defe35eb3fe346627eb492473
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2245610
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68374}

Bug: v8:10564
Change-Id: Ibeaa43d9db087d02d8f4d3688fc1f6da41691a60
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2216931Reviewed-by: Shu-yu Guo <syg@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68373}

Bug: v8:9909
Change-Id: Ica96c2f373b4d90209c8d144486f423f1d8f0859
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2235548
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68372}

- Makes conversion::NonNumberToNumber, NonNumberToNumeric, and
  ToNumeric transitioning builtins. Otherwise, these turn into
  macro invocations, which made several math.tq builtins much
  longer.

Bug: chromium:1094228
Change-Id: Iefb6821ee59f61c11029150c0de4a1bcbd18e721
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2243195
Commit-Queue: Bill Budge <bbudge@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68371}

This is in anticipation of more complex type names coming from the new
proposals.

Change-Id: I1e5b8bd8c5b3edb5b603d36f6c5e9a787ebad504
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2243215
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68370}

As a drive-by, change an if(...) else UNREACHABLE into a CHECK(...).

Change-Id: I6440191c690f36444faa89ac0f7f7dde51ebba3f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2237143Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68369}

Bug: v8:10604
Change-Id: If66656017e53da34aa69bbe19d915df08cf6f332
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2246564
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68368}

Bug: chromium:1056170
Change-Id: I92b36c8ac3d31837729f2e1ce9f3c756a6270da1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2248182
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Auto-Submit: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68367}

- 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}

Change-Id: I3d2da18477df775b6ecc8e358a02f4e838961831
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2241522
Commit-Queue: Georgia Kouveli <georgia.kouveli@arm.com>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68365}

Changes:
- Simplify and generalize ToValueTypeString.
- Fix some error messages in msjunit so that they reflect the underlying
  error better.
- Change 'exn' -> 'exnref' to match exception-handling proposal.

Bug: v8:7581
Change-Id: I264f6c9aa598a57f39d5a4d01399af64db83a2b9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2243214
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68364}

This is in anticipation of more reference types from various proposals
being implemented.

Change-Id: I740ceeb3b6d6fc484a61f9ebee2181dbd6694440
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2243213Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68363}

Avoid spawning low-priority tasks for tier-up, since low-priority tasks
map to the BEST_EFFORT priority in chrome, which will severly delay
execution of the tasks and not execute them even if background threads
are idle (see linked bug).

We should look into reverting this once the gin platform implementation
(or task scheduling) is adjusted to execute low-priority background
tasks more reliably.

R=ahaas@chromium.org

Bug: chromium:1094928
Change-Id: I9e84eeedc7b83bfd17edb1cd09a0084770b20eda
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2247645Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68362}

Rolling v8/build: https://chromium.googlesource.com/chromium/src/build/+log/908ea81..a980f85

Rolling v8/buildtools: https://chromium.googlesource.com/chromium/src/buildtools/+log/574cbd5..3200e0f

Rolling v8/buildtools/linux64: git_revision:9a0496a74efd13c1bb2abd866d8a227404615068..git_revision:fbe7aec770944d17c9f3006f6cbb5c19e8cd43ea

Rolling v8/third_party/aemu-linux-x64: VTMne1aEixrBYfQxsfnRBgzudRPhjV-iUQeXgznyNqgC..T98d0T9VlsHV98PPahwzBa8kF94z5dghLKOTUDCTmwYC

Rolling v8/third_party/catapult: https://chromium.googlesource.com/catapult/+log/b919b00..9253b25

Rolling v8/third_party/depot_tools: https://chromium.googlesource.com/chromium/tools/depot_tools/+log/03705f6..e364dd8

Rolling v8/tools/clang: https://chromium.googlesource.com/chromium/src/tools/clang/+log/79a0420..0d67b22

TBR=machenbach@chromium.org,tmrts@chromium.org,v8-waterfall-sheriff@grotations.appspotmail.com

Change-Id: Ibe96d7bb6c8b4b359698446a3087e4d9c1668704
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2246735Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Commit-Queue: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#68361}