deps: update V8 to 8.1

[mmarchini]

Chrome release date: Mar 17th, 2020.

There's one outstanding issue on 8.0 (nodejs/node-v8#120), but it might not be worth blocking the upgrade because of that (we're unlikely to see that issue outside very specific, synthetic test cases).

Depends on:

• build: enable backtrace when V8 is built for PPC and S390x #32113
• test: update tests for larger Buffers #32114
• test: warn when inspector process crashes #32133
• build: workaround for gclient python3 issues #32140
• test: workaround for V8 8.1 inspector pause issue #32234
• test: make test-memory-usage predictable #32239

Current failing tests and builds:

• sequential/test-inspector-break-when-eval is flaky (likely the same as nodejs/node-v8#120)
  • Child process is crashing with SIGSEGV, so it's likely the same issue.
• Removed MemoryMeasurement::Request::= being called (only Windows is complaining)
• ASAN build is broken on CI (skip failures deps: update V8 to 8.1 #32116 (comment))

Flaky tests (possibly introduced here):

• sequential/test-inspector-break-when-eval also giving an assertion error sometimes
  • Subprocess failed on timers.js
• sequential/test-heap-prof timeout
• parallel/test-repl-history-navigation
• parallel/test-memory-usage
  • being tracked on memory related test failed on v8 8.2 node-v8#144
  • Fixed with test: make test-memory-usage predictable #32239
• sequential/test-cpu-prof-drained might be flaky
  • The assert failed because an error was thrown in the subprocess, causing the wrong stack to be sampled
  • The subprocess failed while trying to load fibonacci.js, apparently on assertSize
  • Looking at the stack again, there's no guarantee an error was thrown, just that the stack was captured by the inspector while opening a file (likely fibonacci.js)
• corrupted double-linked on arm

Flaky tests (seen before)

• sequential/test-worker-prof
• sequential/test-perf-hooks
• parallel/test-tls-ticket-cluster
• parallel/test-worker-memory
• parallel/test-worker-message-port-message-before-close
• sequential/test-timers-blocking-callback
• wasi/test-wasi
• sequential/test-cpu-prof-dir-worker
• parallel/test-inspector-connect-main-thread

[Flarna]

@mmarchini I expect this is preparation for Node.js 14.
Or is it planned to move 13.x also further than 7.9?

[mmarchini]

@gengjiawen thanks, I cherry picked that pull request as well.

@Flarna my main goal is to upgrade master so we don't fall too behind from V8, if we can get it working on time it should make the cut for v14. AFAIK there was no planning/roadmap of V8 version for v13.x, and I believe it will stay on 7.9 (but if someone successfully backports 8.0 or 8.1 to v13.x before April/May, I don't think collaborators would block it).

@targos yes, most errors we're seeing right now are related to the MemoryMeasurement API which we started using on Node.js a couple weeks ago. I'll investigate further today, should be able to fix at least one of the errors we're getting on node-v8 as well.