Download driver for components/download.

content/browser/download/download_item_impl.cc

Index: content/browser/download/download_item_impl.cc
diff --git a/content/browser/download/download_item_impl.cc b/content/browser/download/download_item_impl.cc
index 1132560218034b46a8b1e4f9f82f8c51bc726877..dccaf11c8316d5e1404abdaf6889485d04ec6bb9 100644
--- a/content/browser/download/download_item_impl.cc
+++ b/content/browser/download/download_item_impl.cc
@@ -203,7 +203,8 @@ DownloadItemImpl::DownloadItemImpl(DownloadItemImplDelegate* delegate,
                                    uint32_t download_id,
                                    const DownloadCreateInfo& info,
                                    const net::NetLogWithSource& net_log)
-    : guid_(base::ToUpperASCII(base::GenerateGUID())),
+    : guid_(info.guid.empty() ? base::ToUpperASCII(base::GenerateGUID())

[qinmin, 2017/05/23 04:21:24]

will this download item be written to the history db? if so, why the GUID
generation logic is here instead of in the history db?

[xingliu, 2017/05/23 16:56:13]

I think this logic happens before writing to history db. Also previously we
generated the uuid here.

I guess the reason to generate uuid here is, the in-memory object still needs a
uuid before db persists.

[qinmin, 2017/05/23 18:12:17]

Sorry, what I am saying is that why not let DownloadItemImpl create the GUID,
and pass it back to the caller of DownloadDriver in onDownloadStarted()?  

+                              : info.guid),
       download_id_(download_id),
       target_disposition_((info.save_info->prompt_for_save_location)
                               ? TARGET_DISPOSITION_PROMPT