Context: I'm trying to get mochitests to pass on the B2G emulator with content process sandboxing (seccomp-bpf) enabled, so that we can enable sandboxing in TBPL. Currently we're allowing open(), but the eventual plan is to make its callers request file access through the parent process, and we don't allow a content process to call mkdir(). Problem: Some of the forms tests use FileUtils to create files (either via MockFilePicker.useAnyFile or directly), and FileUtils tries to create a file's enclosing directory even if it already exists. I've attached one possible solution, which avoids trying to create TmpD, under the assumption that it will already exist at this point. I've tested this assumption with a try run: https://tbpl.mozilla.org/?tree=Try&rev=508f4e0290c1 Thoughts?

Comment on attachment 828969 [details] [diff] [review] bugNNNNNN-seccomp-mochitest-mkdir.diff I'm thinking we can check this in now, to unblock getting seccomp on tinderbox, and fix things for real later.

Improving commit message; content of patch unchanged. Carrying over r=sicking.

→ b2g-inbound.