Validate origins when generating subdomain tokens

url/features.gni

Index: url/features.gni
diff --git a/url/features.gni b/url/features.gni
index 3b55cc75caf2ea9947ea86cdc26ff019eadc3296..3e0b75bca0f241438c333423d0a67b9eb033e3db 100644
--- a/url/features.gni
+++ b/url/features.gni
@@ -5,7 +5,12 @@
 # Features used by targets inside and outside of |url|.
 # For details see declare_args() in build/config/BUILDCONFIG.gn.
 declare_args() {
-  # Enables the use of ICU alternatives in lieu of ICU. The flag is used
-  # for Cronet to reduce the size of the Cronet binary.
+  # Enables the use of ICU alternatives in lieu of ICU for the target toolchain.
+  # The flag is used for Cronet to reduce the size of the Cronet binary.
   use_platform_icu_alternatives = false
 }
+
+# Never use platform icu for host toolchain.
+# E.g. Don't apply this for host binaries when target_os = "android".
+use_platform_icu_alternatives =
+    use_platform_icu_alternatives && current_toolchain == default_toolchain