Add extra headers argument so we don't pass headers in the body.

content/browser/download/mhtml_extra_parts_impl.cc

 // Copyright 2017 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 "content/browser/download/mhtml_extra_parts_impl.h"
 
 namespace {
 // Only the address of this variable is used.  It is used as a key to UserData.
 const int kMHTMLExtraPartsKey = 0;
 }
 
 namespace content {
 
+MHTMLExtraDataPart::MHTMLExtraDataPart() = default;
+
+MHTMLExtraDataPart::~MHTMLExtraDataPart() = default;
+
+MHTMLExtraDataPart::MHTMLExtraDataPart(const MHTMLExtraDataPart& other) =
+    default;
+
 MHTMLExtraPartsImpl::MHTMLExtraPartsImpl() = default;
 
 MHTMLExtraPartsImpl::~MHTMLExtraPartsImpl() = default;
 
 MHTMLExtraParts* MHTMLExtraParts::FromWebContents(WebContents* contents) {
   // Get the MHTMLExtraPartsImpl from the web contents.
   MHTMLExtraPartsImpl* extra_data_impl = static_cast<MHTMLExtraPartsImpl*>(
       contents->GetUserData(&kMHTMLExtraPartsKey));
 
   // If we did not have one on the web contents already, make one and put it on
   // the web contents.
   if (extra_data_impl == nullptr) {
     extra_data_impl = new MHTMLExtraPartsImpl();
     contents->SetUserData(&kMHTMLExtraPartsKey,
                           std::unique_ptr<MHTMLExtraParts>(
                               static_cast<MHTMLExtraParts*>(extra_data_impl)));
   }
   return static_cast<MHTMLExtraParts*>(extra_data_impl);
 }
 
 int64_t MHTMLExtraPartsImpl::size() {
   return parts_.size();
 }
 
 void MHTMLExtraPartsImpl::AddExtraMHTMLPart(const std::string& content_type,
                                             const std::string& content_location,
+                                            const std::string& extra_headers,
                                             const std::string& body) {
   MHTMLExtraDataPart part;
   part.content_type = content_type;
   part.content_location = content_location;
+  part.extra_headers = extra_headers;
   part.body = body;
 
   // Add this part to the list of parts to be saved out when the file is
   // written.
   parts_.push_back(part);
 }
 
 }  // namespace content