Added an ActivationReason parameter to ActivationChangeObserver::OnWindowActivated(...).

ash/wm/mru_window_tracker.cc

Index: ash/wm/mru_window_tracker.cc
diff --git a/ash/wm/mru_window_tracker.cc b/ash/wm/mru_window_tracker.cc
index 2c38e0d61a5f9c80816fa10da950a287d7bef026..00e1773313884235def30939470aa317b40409b8 100644
--- a/ash/wm/mru_window_tracker.cc
+++ b/ash/wm/mru_window_tracker.cc
@@ -174,8 +174,10 @@ void MruWindowTracker::SetActiveWindow(aura::Window* active_window) {
   mru_windows_.push_front(active_window);
 }
 
-void MruWindowTracker::OnWindowActivated(aura::Window* gained_active,
-                                         aura::Window* lost_active) {
+void MruWindowTracker::OnWindowActivated(
+    aura::client::ActivationChangeObserver::ActivationReason reason,
+    aura::Window* gained_active,
+    aura::Window* lost_active) {
   if (!ignore_window_activations_)
     SetActiveWindow(gained_active);
 }