Glue parallel download job and download file together.

content/browser/download/mock_download_file.h

Index: content/browser/download/mock_download_file.h
diff --git a/content/browser/download/mock_download_file.h b/content/browser/download/mock_download_file.h
index d982da06cf7281263782b74261b2e45f3e55de90..4bdd1ae6ca2fc57333022363f7a5bebe879724b4 100644
--- a/content/browser/download/mock_download_file.h
+++ b/content/browser/download/mock_download_file.h
@@ -30,9 +30,12 @@ class MockDownloadFile : public DownloadFile {
   // DownloadFile functions.
   MOCK_METHOD1(Initialize, void(const InitializeCallback&));
   void AddByteStream(std::unique_ptr<ByteStreamReader> stream_reader,
-                     int64_t offset) override;
-  MOCK_METHOD2(DoAddByteStream,
-               void(ByteStreamReader* stream_reader, int64_t offset));
+                     int64_t offset,
+                     int64_t length) override;
+  MOCK_METHOD3(DoAddByteStream,
+               void(ByteStreamReader* stream_reader,
+                    int64_t offset,
+                    int64_t length));
   MOCK_METHOD2(AppendDataToFile, DownloadInterruptReason(
       const char* data, size_t data_len));
   MOCK_METHOD1(Rename, DownloadInterruptReason(