Glue parallel download job and download file together.

content/browser/download/download_file_impl.cc

Index: content/browser/download/download_file_impl.cc
diff --git a/content/browser/download/download_file_impl.cc b/content/browser/download/download_file_impl.cc
index e4ec806f7718c8b4de357eb9977f329a852834a7..c47621b8b103bbf8ccf570e0bad1f9860228aceb 100644
--- a/content/browser/download/download_file_impl.cc
+++ b/content/browser/download/download_file_impl.cc
@@ -41,16 +41,18 @@ const int kInitialRenameRetryDelayMs = 200;
 // Number of times a failing rename is retried before giving up.
 const int kMaxRenameRetries = 3;
 
-DownloadFileImpl::SourceStream::SourceStream(int64_t offset, int64_t length)
-    : offset_(offset), length_(length), bytes_written_(0), finished_(false) {}
+DownloadFileImpl::SourceStream::SourceStream(
+    int64_t offset,
+    int64_t length,
+    std::unique_ptr<ByteStreamReader> stream_reader)
+    : offset_(offset),
+      length_(length),
+      bytes_written_(0),
+      finished_(false),
+      stream_reader_(std::move(stream_reader)) {}
 
 DownloadFileImpl::SourceStream::~SourceStream() = default;
 
-void DownloadFileImpl::SourceStream::SetByteStream(
-    std::unique_ptr<ByteStreamReader> stream_reader) {
-  stream_reader_ = std::move(stream_reader);
-}
-
 void DownloadFileImpl::SourceStream::OnWriteBytesToDisk(int64_t bytes_write) {
   bytes_written_ += bytes_write;
 }
@@ -75,9 +77,8 @@ DownloadFileImpl::DownloadFileImpl(
       observer_(observer),
       weak_factory_(this) {
   source_streams_[save_info_->offset] = base::MakeUnique<SourceStream>(
-      save_info_->offset, DownloadSaveInfo::kLengthFullContent);
-  DCHECK(source_streams_.size() == static_cast<size_t>(1));
-  source_streams_[save_info_->offset]->SetByteStream(std::move(stream_reader));
+      save_info_->offset, DownloadSaveInfo::kLengthFullContent,

[qinmin, 2017/03/17 07:54:36]

actually, this is no longer true. For resumption, the length might not be
DownloadSaveInfo::kLengthFullContent.

see
https://cs.chromium.org/chromium/src/content/browser/download/download_item_i....

You either need to remove that line to make the initial request half open, or
set the length here.

[xingliu, 2017/03/17 19:08:25]

Good point, done.

+      std::move(stream_reader));
 
   download_item_net_log.AddEvent(
       net::NetLogEventType::DOWNLOAD_FILE_CREATED,
@@ -120,7 +121,7 @@ void DownloadFileImpl::Initialize(const InitializeCallback& callback) {
   // Primarily to make reset to zero in restart visible to owner.
   SendUpdate();
 
-  // Initial pull from the straw.
+  // Initial pull from the straw from all source streams.
   for (auto& source_stream : source_streams_)
     RegisterAndActivateStream(source_stream.second.get());
 
@@ -131,16 +132,17 @@ void DownloadFileImpl::Initialize(const InitializeCallback& callback) {
 
 void DownloadFileImpl::AddByteStream(
     std::unique_ptr<ByteStreamReader> stream_reader,
-    int64_t offset) {
+    int64_t offset,
+    int64_t length) {
   DCHECK_CURRENTLY_ON(BrowserThread::FILE);
+  DCHECK(source_streams_.find(offset) == source_streams_.end());
 
-  // The |source_streams_| must have an existing entry for the stream reader.
-  auto current_source_stream = source_streams_.find(offset);
-  DCHECK(current_source_stream != source_streams_.end());
-  SourceStream* stream = current_source_stream->second.get();
-  stream->SetByteStream(std::move(stream_reader));
+  source_streams_[offset] =
+      base::MakeUnique<SourceStream>(offset, length, std::move(stream_reader));
 
-  RegisterAndActivateStream(stream);
+  // If the file is initialized, start to write data, or wait until file opened.
+  if (file_.in_progress())
+    RegisterAndActivateStream(source_streams_[offset].get());
 }
 
 DownloadInterruptReason DownloadFileImpl::WriteDataToFile(int64_t offset,