Add missing header from core.gni

Change-Id: I106364cb3875640a637476998dc1d3936566f0ab
Reviewed-on: https://skia-review.googlesource.com/126120
Commit-Queue: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Reviewed-by: Herb Derby <herb@google.com>
1 file changed