Limit parallel download to http GET requests.

content/browser/download/download_job_factory.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/download_job_factory.h"
 
 #include <memory>
 
 #include "base/memory/ptr_util.h"
 #include "content/browser/download/download_item_impl.h"
@@ skipping 10 matching lines @@
 
 // Returns if the download can be parallelized.
 bool IsParallelizableDownload(const DownloadCreateInfo& create_info) {
   // To enable parallel download, following conditions need to be satisfied.
   // 1. Feature |kParallelDownloading| enabled.
   // 2. Strong validators response headers. i.e. ETag and Last-Modified.
   // 3. Accept-Ranges header.
   // 4. Content-Length header.
   // 5. Content-Length is no less than the minimum slice size configuration.
   // 6. HTTP/1.1 protocol, not QUIC nor HTTP/1.0.
+  // 7. HTTP or HTTPS scheme with GET method in the initial request.
 
   // Etag and last modified are stored into DownloadCreateInfo in
   // DownloadRequestCore only if the response header complies to the strong
   // validator rule.
   bool has_strong_validator =
       !create_info.etag.empty() || !create_info.last_modified.empty();
   bool has_content_length = create_info.total_bytes > 0;
   bool satisfy_min_file_size =
       create_info.total_bytes >= GetMinSliceSizeConfig();
   bool satisfy_connection_type = create_info.connection_info ==
                                  net::HttpResponseInfo::CONNECTION_INFO_HTTP1_1;
+  bool http_get_method =
+      create_info.method == "GET" && create_info.url().SchemeIsHTTPOrHTTPS();
 
   bool is_parallelizable = has_strong_validator && create_info.accept_range &&

[qinmin, 2017/05/22 21:24:50]

you need to add a new UMA enum for this

[xingliu, 2017/05/22 22:01:49]

Done.

                            has_content_length && satisfy_min_file_size &&
-                           satisfy_connection_type;
+                           satisfy_connection_type && http_get_method;
 
   if (!IsParallelDownloadEnabled())
     return is_parallelizable;
 
   RecordParallelDownloadCreationEvent(
       is_parallelizable
           ? ParallelDownloadCreationEvent::STARTED_PARALLEL_DOWNLOAD
           : ParallelDownloadCreationEvent::FELL_BACK_TO_NORMAL_DOWNLOAD);
 
   if (!has_strong_validator) {
@@ skipping 34 matching lines @@
                                                  std::move(req_handle),
                                                  create_info);
   }
 
   // An ordinary download job.
   return base::MakeUnique<DownloadJobImpl>(download_item, std::move(req_handle),
                                            is_parallelizable);
 }
 
 }  // namespace