Add new UMA stats for parallelizable download

content/browser/download/download_job_factory.cc

Index: content/browser/download/download_job_factory.cc
diff --git a/content/browser/download/download_job_factory.cc b/content/browser/download/download_job_factory.cc
index d0a7c7c9210a757facfc1ad4a0b88d82534a02c4..4edb053f2562ad83909b42167ddb6f29f5c898d6 100644
--- a/content/browser/download/download_job_factory.cc
+++ b/content/browser/download/download_job_factory.cc
@@ -19,7 +19,7 @@ namespace content {
 
 namespace {
 
-// Returns if the download should be a parallel download.
+// Returns if the download can be parallelized.
 bool ShouldUseParallelDownload(const DownloadCreateInfo& create_info) {

[xingliu, 2017/04/19 02:18:11]

nit: Maybe also change the function name?

[qinmin, 2017/04/19 22:42:33]

Done.

   // To enable parallel download, following conditions need to be satisfied.
   // 1. Feature |kParallelDownloading| enabled.
@@ -28,8 +28,6 @@ bool ShouldUseParallelDownload(const DownloadCreateInfo& create_info) {
   // 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.
-  if (!base::FeatureList::IsEnabled(features::kParallelDownloading))
-    return false;
 
   // Etag and last modified are stored into DownloadCreateInfo in
   // DownloadRequestCore only if the response header complies to the strong
@@ -46,6 +44,9 @@ bool ShouldUseParallelDownload(const DownloadCreateInfo& create_info) {
       has_strong_validator && create_info.accept_range && has_content_length &&
       satisfy_min_file_size && satisfy_connection_type;
 
+  if (!base::FeatureList::IsEnabled(features::kParallelDownloading))
+    return should_use_parallel_download;
+
   RecordParallelDownloadCreationEvent(
       should_use_parallel_download
           ? ParallelDownloadCreationEvent::STARTED_PARALLEL_DOWNLOAD
@@ -81,16 +82,18 @@ std::unique_ptr<DownloadJob> DownloadJobFactory::CreateJob(
     DownloadItemImpl* download_item,
     std::unique_ptr<DownloadRequestHandleInterface> req_handle,
     const DownloadCreateInfo& create_info) {
+  bool is_parallizable = ShouldUseParallelDownload(create_info);
   // Build parallel download job.
-  if (ShouldUseParallelDownload(create_info)) {
+  if (base::FeatureList::IsEnabled(features::kParallelDownloading) &&
+      is_parallizable) {
     return base::MakeUnique<ParallelDownloadJob>(download_item,
                                                  std::move(req_handle),
                                                  create_info);
   }
 
   // An ordinary download job.
-  return base::MakeUnique<DownloadJobImpl>(download_item,
-                                           std::move(req_handle));
+  return base::MakeUnique<DownloadJobImpl>(download_item, std::move(req_handle),
+                                           is_parallizable);
 }
 
 }  // namespace