Fix race condition where chrome.tabs.executeScript sometimes wouldn't

chrome/renderer/navigation_state.cc

Index: chrome/renderer/navigation_state.cc
diff --git a/chrome/renderer/navigation_state.cc b/chrome/renderer/navigation_state.cc
index fe1c6d9cf0ecdbdb8208238cd6a9b65aadee961b..899c2d224820d6fc0c32296cb7926bae159b5455 100644
--- a/chrome/renderer/navigation_state.cc
+++ b/chrome/renderer/navigation_state.cc
@@ -15,6 +15,11 @@ void NavigationState::set_user_script_idle_scheduler(
   user_script_idle_scheduler_.reset(scheduler);
 }
 
+void NavigationState::swap_user_script_idle_scheduler(
+    NavigationState* state) {
+  user_script_idle_scheduler_.swap(state->user_script_idle_scheduler_);
+}
+
 void NavigationState::set_password_form_data(webkit_glue::PasswordForm* data) {
   password_form_data_.reset(data);
 }