fix formdata arg validation

[KhafraDev]

var fd = new FormData()

fd.set('key', new Blob([]), undefined)
fd.get('key').name // should be 'blob'

fd.append('key1', new Blob([]), undefined)
fd.get('key1').name // should be 'blob'

I painfully found out that the wpts are not extensive

[Uzlopak]

cant this be at line 140?

[KhafraDev]

No. The webidl stuff occurs before the steps, but the step is also not needed because js doesn't have method overrides (hence the weird webidl here).

The set(name, value) and set(name, blobValue, filename) method steps are:

The first step is telling us to set value to "blobValue" if there were 3 arguments passed, otherwise do nothing. "value" is only ever "value" here.

[mcollina]

lgtm

[github-actions]

The backport to v6.x failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-v6.x v6.x
# Navigate to the new working tree
cd .worktrees/backport-v6.x
# Create a new branch
git switch --create backport-3529-to-v6.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 e0714063deb24f4887b00e0b90060ac71190b273
# Push it to GitHub
git push --set-upstream origin backport-3529-to-v6.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-v6.x

Then, create a pull request where the base branch is v6.x and the compare/head branch is backport-3529-to-v6.x.

[Uzlopak]

@KhafraDev
I think this is worth to get backported