Treat exact domain match cookies on public suffixes as host cookies.

net/cookies/cookie_util.cc

Index: net/cookies/cookie_util.cc
diff --git a/net/cookies/cookie_util.cc b/net/cookies/cookie_util.cc
index b9c7e8d601f8ed2e3c4d8b3eb07c8e1d0c5ffdae..4071e6fd380f6482c71f06739fc6615934f995ec 100644
--- a/net/cookies/cookie_util.cc
+++ b/net/cookies/cookie_util.cc
@@ -63,8 +63,19 @@ bool GetCookieDomainWithString(const GURL& url,
   const std::string url_scheme(url.scheme());
   const std::string url_domain_and_registry(
       GetEffectiveDomain(url_scheme, url_host));
-  if (url_domain_and_registry.empty())
-    return false;  // IP addresses/intranet hosts can't set domain cookies.
+  if (url_domain_and_registry.empty()) {
+    // We match IE/Firefox by treating an exact match between the domain
+    // attribute and the request host to be treated as a host cookie.
+    if (url_host == domain_string) {
+      *result = url_host;
+      DCHECK(DomainIsHostOnly(*result));
+      return true;
+    }
+
+    // Otherwise, IP addresses/intranet hosts/public suffixes can't set
+    // domain cookies.
+    return false;
+  }
   const std::string cookie_domain_and_registry(
       GetEffectiveDomain(url_scheme, cookie_domain));
   if (url_domain_and_registry != cookie_domain_and_registry)