Add certificate pin for gstatic.cn

Add gstatic.cn to the Google certificate pin list.

TBR=nharper@chromium.org

Change-Id: I8a99c6a9c98c6b2f38b83050972a700953bb886b
Reviewed-on: https://chromium-review.googlesource.com/943824Reviewed-by: Eric Lawrence <elawrence@chromium.org>
Reviewed-by: Adam Langley <agl@chromium.org>
Commit-Queue: Eric Lawrence <elawrence@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540344}

net/http/transport_security_state_static.json

@@ -641,6 +641,7 @@
     { "name": "googleweblight.com", "policy": "google", "include_subdomains": true, "pins": "google" },
     { "name": "google.ws", "policy": "google", "include_subdomains": true, "pins": "google" },
     { "name": "gstatic.com", "policy": "google", "include_subdomains": true, "pins": "google" },
+    { "name": "gstatic.cn", "policy": "google", "include_subdomains": true, "pins": "google" },
     { "name": "gvt1.com", "policy": "google", "include_subdomains": true, "pins": "google" },
     { "name": "static.googleadsserving.cn", "policy": "google", "include_subdomains": true, "pins": "google" },
     { "name": "urchin.com", "policy": "google", "include_subdomains": true, "pins": "google" },