DRAFT CL: Add FrameNavigationEntry and track subframe session histories.

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 b704b8e93066cae1be09fdb882a534f5d2f115c7..b7c6b7d8e43a4cc9e1569543db47d101cf51b961 100644
--- a/content/public/common/frame_navigate_params.h
+++ b/content/public/common/frame_navigate_params.h
@@ -25,8 +25,16 @@ struct CONTENT_EXPORT FrameNavigateParams {
   // anytime a new session history entry is created. This means you'll get new
   // page IDs for user actions, and the old page IDs will be reloaded when
   // iframes are loaded automatically.
+  // TODO(creis): Update comment.  This is now just for associating with a
+  // top-level NavigationEntry for history navigations.  It's -1 for new
+  // navigations, and the browser will figure out where it belongs.
   int32 page_id;
 
+  // Identifies new navigations within a frame.
+  // TODO(creis): Elaborate.
+  int64 item_sequence_number;
+  int64 document_sequence_number;
+
   // URL of the page being loaded.
   GURL url;