Support for BigBuffer in IPC broken in 6.x and nightly

[issacgerges]

Preflight Checklist

• I have read the Contributing Guidelines for this project.
• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for an issue that matches the one I want to file, without success.

Issue Details

• Electron Version:
  7.0.0-nightly.20190611
• Operating System:
  MacOS 10.14.5
• Last Known Working Electron version:
  v5.0.3

Expected Behavior

With the merge of https://chromium.googlesource.com/chromium/src/+/4c5bd80e, legacy ipc internally uses BigBuffer and should support large messages.

Actual Behavior

Electron crashes when ipc.send is called with a large arg (~134mb)

To Reproduce

The following can be opened in electron-fiddle to reproduce the issue

https://gist.github.com/issacgerges/370a76335fd699930c43bde5cbeb41b7

[issacgerges]

Using lldb it looks like the 6.x error was introduced with this change https://chromium.googlesource.com/chromium/src/+/66.0.3359.158/mojo/edk/system/node_channel.cc#900

The 7.x-nightly error appears to be unrelated, due to porting away from legacy ipc

[coreh]

Yeah, perhaps there is a way we can set max_message_num_bytes?

I tried using something like

app.commandLine.appendSwitch('max_message_num_bytes', '4096000000');

But it doesn't seem to be recognized

Edit: Looks like it's hardcoded to kMaximumMessageSize:

https://github.com/chromium/chromium/blob/8a7f35f9ff2de4a52d053b9a15969663077c2178/content/app/mojo/mojo_init.cc#L24-L25

[nornagon]

@issacgerges hm.. i'm not sure how that change could result in an error in 6.x since it was introduced in Chrome 66?

I think the right way to handle this would be to add something like ipcRenderer.sendBuffer('channel', args, buf) that uses the mojo_base.mojom.BigBuffer data type under the hood, rather than trying to make send support arbitrarily large data. @issacgerges I'd be happy to help you out getting a PR up for that :)

[nornagon]

I don't have time to work on this at the moment, but I'm happy to help someone else who wants to tackle it.

[codebytere]

Resolved by #20214.