Remove OS condition from isolate files

Change-Id: Ib8e7d4dd40bb8e59b0901ef40351ccae924749d2
Reviewed-on: https://skia-review.googlesource.com/c/196384
Commit-Queue: Ben Wagner <benjaminwagner@google.com>
Reviewed-by: Eric Boren <borenet@google.com>
4 files changed