Don't check is_ios in chrome/, it's always false there.

chrome/common/net/BUILD.gn

Index: chrome/common/net/BUILD.gn
diff --git a/chrome/common/net/BUILD.gn b/chrome/common/net/BUILD.gn
index b21b2ff891cf820e2d53ec8bf1735d723ce66afa..73bc725e065e547ec9ef628da175b01e7d4edb1e 100644
--- a/chrome/common/net/BUILD.gn
+++ b/chrome/common/net/BUILD.gn
@@ -4,6 +4,8 @@
 
 import("//build/config/crypto.gni")
 
+assert(!is_ios, "Chromium/iOS shouldn't use anything in //chrome")
+
 static_library("net") {
   sources = [
     "net_resource_provider.cc",
@@ -28,11 +30,7 @@ static_library("net") {
     "//ui/base",
   ]
 
-  if (is_ios) {
-    sources -= [ "net_resource_provider.cc" ]
-  }
-
-  if (is_android || is_ios) {
+  if (is_android) {
     sources -= [ "x509_certificate_model.cc" ]
   }