Nevermind, /home probably means you’re on Linux. I think Ubuntu has a similar restriction against ptracing non-child processes. You have to do silly stuff like:
echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope
(lldb) attach -p 11275
Process 11275 stopped
Executable module set to "/home/tfarina/chromium/src/out/Debug/chrome".
Architecture set to: x86_64-unknown-linux.