Fix a -Wunused-function warning in gn builds.

BUG=chromium:573250

Review URL: https://codereview.webrtc.org/1552863002

Cr-Original-Commit-Position: refs/heads/master@{#11145}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 06689a1d17c15002e02d08e4299b6842693431cd
diff --git a/base/network.cc b/base/network.cc
index 1f413b3..488c475 100644
--- a/base/network.cc
+++ b/base/network.cc
@@ -119,6 +119,7 @@
   }
 }
 
+#if !defined(__native_client__)
 bool IsIgnoredIPv6(const InterfaceAddress& ip) {
   if (ip.family() != AF_INET6) {
     return false;
@@ -143,6 +144,7 @@
 
   return false;
 }
+#endif  // !defined(__native_client__)
 
 }  // namespace