Fix nacl_tuple "Undefined identifier" gn gen failure for arm64
Fix nacl_tuple "Undefined identifier" gn gen failure for arm64

BUG=568883

Review URL: https://codereview.chromium.org/1517203002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#365535}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk