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

chrome/browser/android/offline_pages/prerendering_offliner.cc

 // Copyright 2016 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 "chrome/browser/android/offline_pages/prerendering_offliner.h"
 
 #include "base/bind.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/sys_info.h"
 #include "chrome/browser/android/offline_pages/offline_page_mhtml_archiver.h"
@@ skipping 76 matching lines @@
     save_page_params.is_background = true;
     // Pass in the original URL if it is different from the last committed URL
     // when redirects occur.
     if (!request.original_url().is_empty())
       save_page_params.original_url = request.original_url();
     else if (save_page_params.url != request.url())
       save_page_params.original_url = request.url();
 
     if (IsOfflinePagesLoadSignalCollectingEnabled()) {
       // Stash loading signals for writing when we write out the MHTML.
-      std::string headers =
-          base::StringPrintf("%s\r\n%s\r\n\r\n", kContentTransferEncodingBinary,
-                             kXHeaderForSignals);
-      std::string body = headers + SerializeLoadingSignalData();
+      // TODO(petewil): Add this data to the BackgroundLoaderOffliner too.
+      std::string extra_headers = base::StringPrintf(
+          "%s\r\n%s", kContentTransferEncodingBinary, kXHeaderForSignals);
+      std::string body = SerializeLoadingSignalData();
       std::string content_type = kContentType;
       std::string content_location = base::StringPrintf(
           "cid:signal-data-%" PRId64 "@mhtml.blink", request.request_id());
 
       content::MHTMLExtraParts* extra_parts =
           content::MHTMLExtraParts::FromWebContents(web_contents);
       DCHECK(extra_parts);
       if (extra_parts != nullptr) {
-        extra_parts->AddExtraMHTMLPart(content_type, content_location, body);
+        extra_parts->AddExtraMHTMLPart(content_type, content_location,
+                                       extra_headers, body);
       }
     }
 
     SavePage(save_page_params, std::move(archiver),
              base::Bind(&PrerenderingOffliner::OnSavePageDone,
                         weak_ptr_factory_.GetWeakPtr(), request));
   } else {
     // Clear pending request and app listener then run completion callback.
     pending_request_.reset(nullptr);
     app_listener_.reset(nullptr);
@@ skipping 203 matching lines @@
 void PrerenderingOffliner::HandleApplicationStateChangeCancel(
     const SavePageRequest& request,
     int64_t offline_id) {
   // This shouldn't be immediate, but account for case where request was reset
   // while waiting for callback.
   if (pending_request_ && pending_request_->request_id() != offline_id)
     return;
   completion_callback_.Run(request, RequestStatus::FOREGROUND_CANCELED);
 }
 }  // namespace offline_pages