Add a build flag to configure bundling of HSTS preload list

net/features.gni

Index: net/features.gni
diff --git a/net/features.gni b/net/features.gni
index 95c718ebadb7edb2a72d3363d3936374c4e4fb3b..c031e3fecdfbd72cde86c4b121c66ae50023ec2b 100644
--- a/net/features.gni
+++ b/net/features.gni
@@ -30,4 +30,13 @@ declare_args() {
 
   # Reporting not used on iOS.
   enable_reporting = !is_ios
+
+  # Whether transport security preload list should be included. This flag should

[lgarron, 2017/07/11 19:29:04]

Nit: "Whether the transport security preload list..."

I would prefer to be more direct rather than mentioning general "tradeoffs" and
a spec. Also, the preload list includes more than HSTS.

How about this?

----------------------------

Include the transport security preload list. This list includes mechanisms (e.g.
HSTS, HPKP) to enforce trusted connections to a significant set of hardcoded
domains. It should not be disabled unless building a subset of the codebase
where several hundred KB of binary size are a large burden, and the application
is willing to take responsibility to make sure that all important connections
use HTTPS.

[xunjieli, 2017/07/11 20:27:34]

Done.

+  # not be changed without examining the risks and tradeoffs.
+  # HTTP strict transport security (HSTS) is defined in
+  # http://tools.ietf.org/html/ietf-websec-strict-transport-sec.
+  # Changing this flag to false will disable bundling of
+  # net/http/transport_security_state_static.json, which enforces domains-
+  # configured HSTS settings.
+  include_transport_security_state_preload_list = true
 }