[Sync] Don't crash for encryption errors

sync/internal_api/syncapi_internal.cc

 // Copyright (c) 2012 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 "sync/internal_api/syncapi_internal.h"
 
 #include "base/memory/scoped_ptr.h"
 #include "sync/protocol/attachments.pb.h"
 #include "sync/protocol/password_specifics.pb.h"
 #include "sync/protocol/sync.pb.h"
@@ skipping 12 matching lines @@
 sync_pb::PasswordSpecificsData* DecryptPasswordSpecifics(
     const sync_pb::EntitySpecifics& specifics, Cryptographer* crypto) {
   if (!specifics.has_password())
     return NULL;
   const sync_pb::PasswordSpecifics& password_specifics = specifics.password();
   if (!password_specifics.has_encrypted())
     return NULL;
   const sync_pb::EncryptedData& encrypted = password_specifics.encrypted();
   scoped_ptr<sync_pb::PasswordSpecificsData> data(
       new sync_pb::PasswordSpecificsData);
+  if (!crypto->CanDecrypt(encrypted))
+    return NULL;
   if (!crypto->Decrypt(encrypted, data.get()))
     return NULL;
   return data.release();
 }
 
 // The list of names which are reserved for use by the server.
 static const char* kForbiddenServerNames[] = { "", ".", ".." };
 
 // When taking a name from the syncapi, append a space if it matches the
 // pattern of a server-illegal name followed by zero or more spaces.
@@ skipping 64 matching lines @@
 
 bool AreAttachmentMetadataEqual(const sync_pb::AttachmentMetadata& left,
                                 const sync_pb::AttachmentMetadata& right) {
   if (left.SerializeAsString() == right.SerializeAsString()) {
     return true;
   }
   return false;
 }
 
 }  // namespace syncer