This adds support for encrypted ONC import

crypto/symmetric_key_win.cc

Index: crypto/symmetric_key_win.cc
diff --git a/crypto/symmetric_key_win.cc b/crypto/symmetric_key_win.cc
index d2034e0304c7bc163ef67704aa90a6a851fae261..3a300fc50bc7e39e80d7db26ddfbd25d592cc6fd 100644
--- a/crypto/symmetric_key_win.cc
+++ b/crypto/symmetric_key_win.cc
@@ -495,7 +495,7 @@ SymmetricKey* SymmetricKey::Import(Algorithm algorithm,
                           raw_key.data(), raw_key.size());
 }
 
-bool SymmetricKey::GetRawKey(std::string* raw_key) {
+bool SymmetricKey::GetRawKey(std::string* raw_key) const {
   // Short circuit for when the key was supplied to the constructor.
   if (!raw_key_.empty()) {
     *raw_key = raw_key_;