net: don't duplicate HPKP hashes when parsing the header.

net/http/http_security_headers.cc

Index: net/http/http_security_headers.cc
diff --git a/net/http/http_security_headers.cc b/net/http/http_security_headers.cc
index 9fc7627cc5e0c676c3461ad4a8340145d5d00ca3..0c3305f6e42731711cd3f77d0f2162e79a571fd6 100644
--- a/net/http/http_security_headers.cc
+++ b/net/http/http_security_headers.cc
@@ -325,7 +325,18 @@ bool ParseHPKPHeader(const std::string& value,
   *include_subdomains = include_subdomains_candidate;
   for (HashValueVector::const_iterator i = pins.begin();
        i != pins.end(); ++i) {
-    hashes->push_back(*i);
+    bool found = false;
+
+    for (HashValueVector::const_iterator j = hashes->begin();
+         j != hashes->end(); ++j) {
+      if (j->Equals(*i)) {
+        found = true;
+        break;
+      }
+    }
+
+    if (!found)
+      hashes->push_back(*i);
   }
 
   return true;