Implement net in GN build.

crypto/BUILD.gn

Index: crypto/BUILD.gn
diff --git a/crypto/BUILD.gn b/crypto/BUILD.gn
index 110868da4c31525010fc03906dc14ef904567c7f..455169c2f2e08f5255703cf417f2aba964e6e198 100644
--- a/crypto/BUILD.gn
+++ b/crypto/BUILD.gn
@@ -264,8 +264,16 @@ group("platform") {
     if (is_linux) {
       # On Linux, we use the system NSS (excepting SSL where we always use our
       # own).
+      #
+      # We always need our SSL header search path to come before the system one
+      # so our versions are used. The libssl target will add the search path we
+      # want, but according to GN's ordering rules, direct_dependent_configs'
+      # search path will get applied before ones inherited from our
+      # dependencies. Therefore, we need to explicitly list our custom libssl's
+      # config here before the system one.
       direct_dependent_configs = [
-        "//third_party/nss:system_nss_no_ssl_config"
+        "//net/third_party/nss/ssl:ssl_config",
+        "//third_party/nss:system_nss_no_ssl_config",
       ]
     } else {
       # Non-Linux platforms use the hermetic NSS from the tree.