Experiment with HSTS preload list filtering.

net/features.gni

Index: net/features.gni
diff --git a/net/features.gni b/net/features.gni
index 12ba0e011c2f0893940ef0394d289251e5e7b21b..bbc22f2674d7b6a4c0f3cb797f05f2e30e01f103 100644
--- a/net/features.gni
+++ b/net/features.gni
@@ -27,4 +27,12 @@ declare_args() {
 
   # Multicast DNS.
   enable_mdns = is_win || is_linux
+
+  # The level of filtering for the HSTS preload list:
+  #  2: Heavy filtering; filter everything except entries that are needed for
+  #                      all targets to build and pass tests.
+  #  1: Moderate filtering; only the above and specificly marked entries are
+  #                         included.
+  #  0: No filtering; all entries are included.
+  hsts_preload_list_filter_level = 1  # Testing
 }