inspector: libuv notification on incoming message

[eugeneo]

Currently Inspector posts a V8 "task" when a message is incoming. To
make sure messages are processed even when no JS is executed (e.g. while
waiting for I/O or timer), inspector will now post a libuv request.

Fixes: #11589

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

Affected core subsystem(s)

inspector

[kfarnung]

The code change looks good. I tested it out on Windows using VSCode and I no longer get the request timeout errors in the console. The breakpoint gets set immediately.

[bnoordhuis]

LGTM with two nits.

[bnoordhuis]

Can you CHECK_EQ(0, uv_async_send(&main_thread_req_)) here?

[bnoordhuis]

A default param might be nicer for the second argument, i.e., function(callback, arg = '--inspect-brk', contents). The string '--inspect' makes the intent clearer at the call site than a boolean does.

Style issue: we generally use camelCase for arguments and locals in JS land.

[eugeneo]

@bnoordhuis Thank you for the review. I addressed the comments.

[eugeneo]

CI: https://ci.nodejs.org/job/node-test-pull-request/6691/

[eugeneo]

Landed as f01fd2a

[MylesBorins]

I would love to see an effort for a wholesale update of the inspect stuff on v6. If not possible please lmk

[eugeneo]

I don't think v6.x has this issue, it was introduced in the refactoring that was never backported...

Is there a list of inspector issues in v6?