Classify navigations without page id in parallel to the existing classifier.

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..f5d0f6133ae37cc3b41f6b10650fa3ff6e40f73f 100644
--- a/content/public/common/frame_navigate_params.h
+++ b/content/public/common/frame_navigate_params.h
@@ -27,6 +27,12 @@ struct CONTENT_EXPORT FrameNavigateParams {
   // iframes are loaded automatically.
   int32 page_id;
 
+  // The unique ID of the NavigationEntry for browser-initiated navigations.
+  // This value was given to the render process in the HistoryNavigationParams
+  // and is being returned by the renderer without it having any idea what it
+  // means.
+  int nav_entry_id;
+
   // URL of the page being loaded.
   GURL url;