Add item and document sequence numbers to FrameNavigationEntry.

content/public/common/frame_navigate_params.h

Index: content/public/common/frame_navigate_params.h
diff --git a/content/public/common/frame_navigate_params.h b/content/public/common/frame_navigate_params.h
index 884a1d1b6d2ff76eb9debc05e0ee453d34908f01..e3b93342eda2c3e2eac1fe4a8023e418a037e9bc 100644
--- a/content/public/common/frame_navigate_params.h
+++ b/content/public/common/frame_navigate_params.h
@@ -33,6 +33,17 @@ struct CONTENT_EXPORT FrameNavigateParams {
   // means. If the navigation was renderer-initiated, this value is 0.
   int nav_entry_id;
 
+  // The item sequence number identifies each stop in the session history.  It
+  // is unique within the renderer process and makes a best effort to be unique
+  // across browser sessions (using a renderer process timestamp).
+  int64 item_sequence_number;
+
+  // The document sequence number is used to identify cross-document navigations
+  // in session history.  It increments for each new document and is unique in
+  // the same way as |item_sequence_number|.  In-page navigations get a new item
+  // sequence number but the same document sequence number.
+  int64 document_sequence_number;
+
   // URL of the page being loaded.
   GURL url;