Remove the extra copy of page id.

content/browser/renderer_host/render_view_host_impl.h

Index: content/browser/renderer_host/render_view_host_impl.h
diff --git a/content/browser/renderer_host/render_view_host_impl.h b/content/browser/renderer_host/render_view_host_impl.h
index f5f3dec861ff47cbce07a926e1ceef524ef31384..4d34cd0da8db44b26734f18cbe87ece82a95e4e4 100644
--- a/content/browser/renderer_host/render_view_host_impl.h
+++ b/content/browser/renderer_host/render_view_host_impl.h
@@ -410,11 +410,6 @@ class CONTENT_EXPORT RenderViewHostImpl
   // See BindingsPolicy for details.
   int enabled_bindings_;
 
-  // The most recent page ID we've heard from the renderer process.  This is
-  // used as context when other session history related IPCs arrive.
-  // TODO(creis): Allocate this in WebContents/NavigationController instead.
-  int32 page_id_;

[Charlie Reis, 2015/05/13 17:17:51]

To get UpdateTitle and UpdateState to work when cross-process navigations may
have recently committed, I think we need each RVH (or RFH?) to know which
NavigationEntry it's on.

We don't need page ID for this (since it's going away), but we need something. 
Unique ID would probably work.

-
   // Tracks whether this RenderViewHost is in an active state.  False if the
   // main frame is pending swap out, pending deletion, or swapped out, because
   // it is not visible to the user in any of these cases.