[Sync] Initial support for encrypting any datatype (no UI hookup yet).

chrome/browser/sync/util/cryptographer.cc

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/base64.h"
 #include "chrome/browser/sync/util/cryptographer.h"
 #include "chrome/browser/password_manager/encryptor.h"
 
 namespace browser_sync {
 
@@ skipping 41 matching lines @@
                                         encrypted->mutable_blob())) {
     NOTREACHED();  // Encrypt should not fail.
     return false;
   }
   return true;
 }
 
 bool Cryptographer::Decrypt(const sync_pb::EncryptedData& encrypted,
                             ::google::protobuf::MessageLite* message) const {
   DCHECK(message);
+  std::string plaintext = DecryptToString(encrypted);
+  return message->ParseFromString(plaintext);
+}
 
+std::string Cryptographer::DecryptToString(
+    const sync_pb::EncryptedData& encrypted) const {
   NigoriMap::const_iterator it = nigoris_.find(encrypted.key_name());
   if (nigoris_.end() == it) {
     NOTREACHED() << "Cannot decrypt message";
-    return false;  // Caller should have called CanDecrypt(encrypt).
+    return std::string("");  // Caller should have called CanDecrypt(encrypt).
   }
 
   std::string plaintext;
   if (!it->second->Decrypt(encrypted.blob(), &plaintext)) {
-    return false;
+    return std::string("");
   }
 
-  return message->ParseFromString(plaintext);
+  return plaintext;
 }
 
 bool Cryptographer::GetKeys(sync_pb::EncryptedData* encrypted) const {
   DCHECK(encrypted);
   DCHECK(!nigoris_.empty());
 
   // Create a bag of all the Nigori parameters we know about.
   sync_pb::NigoriKeyBag bag;
   for (NigoriMap::const_iterator it = nigoris_.begin(); it != nigoris_.end();
        ++it) {
@@ skipping 161 matching lines @@
         continue;
       }
       nigoris_[key.name()] = make_linked_ptr(new_nigori.release());
     }
   }
   DCHECK(nigoris_.end() != nigoris_.find(default_key_name));
   default_nigori_ = &*nigoris_.find(default_key_name);
 }
 
 }  // namespace browser_sync