Add a flag to require a user gesture to add an entry to the back/forward list.

content/browser/renderer_host/render_view_host_impl.cc

Index: content/browser/renderer_host/render_view_host_impl.cc
diff --git a/content/browser/renderer_host/render_view_host_impl.cc b/content/browser/renderer_host/render_view_host_impl.cc
index 99a5c54e389e41952fa0d5bddb15e545b5b3247b..6d4e908768ef7c67faf0459c529671e9dbc690ce 100644
--- a/content/browser/renderer_host/render_view_host_impl.cc
+++ b/content/browser/renderer_host/render_view_host_impl.cc
@@ -475,6 +475,9 @@ WebPreferences RenderViewHostImpl::ComputeWebkitPrefs() {
   prefs.pinch_overlay_scrollbar_thickness = 10;
   prefs.use_solid_color_scrollbars = ui::IsOverlayScrollbarEnabled();
 
+  prefs.history_entry_requires_user_gesture =
+      command_line.HasSwitch(switches::kHistoryEntryRequiresUserGesture);
+
 #if defined(OS_ANDROID)
   // On Android, user gestures are normally required, unless that requirement
   // is disabled with a command-line switch or the equivalent field trial is