Store the UploadData identifier in NavigationEntryImpl.

content/common/view_messages.h

Index: content/common/view_messages.h
diff --git a/content/common/view_messages.h b/content/common/view_messages.h
index 23fa018c5ea79ef00d0ea2fcc58c4421834297b8..248c18c86aaf026f680ce142f675e8a335817533 100644
--- a/content/common/view_messages.h
+++ b/content/common/view_messages.h
@@ -443,6 +443,9 @@ IPC_STRUCT_BEGIN_WITH_PARENT(ViewHostMsg_FrameNavigate_Params,
   // True if this was a post request.
   IPC_STRUCT_MEMBER(bool, is_post)
 
+  // The POST body identifier. -1 if it doesn't exist.

[cbentzel, 2012/02/01 22:02:13]

I considered removing the |is_post| field in favor of just the |post_id| field,
but was concerned that there may be cases where the method is "POST" but there
is no WebHistoryItem or httpBody attached to that item. See render_view_impl.cc
for that.

+  IPC_STRUCT_MEMBER(int64, post_id)
+
   // Whether the frame navigation resulted in no change to the documents within
   // the page. For example, the navigation may have just resulted in scrolling
   // to a named anchor.