Changes instant so that the newly created tab has a new id. Doing

chrome/browser/tab_contents/navigation_controller.cc

Index: chrome/browser/tab_contents/navigation_controller.cc
diff --git a/chrome/browser/tab_contents/navigation_controller.cc b/chrome/browser/tab_contents/navigation_controller.cc
index 9439f2118e9c73ddf82aadf22534a268c197d0a8..f294535e7942f5cd8713c7941932ddc3726ee9b5 100644
--- a/chrome/browser/tab_contents/navigation_controller.cc
+++ b/chrome/browser/tab_contents/navigation_controller.cc
@@ -975,14 +975,6 @@ void NavigationController::CopyStateFromAndPrune(NavigationController* source) {
     if (last_committed_entry_index_ != -1)
       last_committed_entry_index_--;
   }
-
-  // Take over the session id from source.
-  session_id_ = source->session_id_;
-
-  // Reset source's session id as we're taking it over. We give it a new id in
-  // case source is added later on, which can happen with instant enabled if the
-  // tab has a before unload handler.
-  source->session_id_ = SessionID();
 }
 
 void NavigationController::PruneAllButActive() {