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

ash/display/display_controller_unittest.cc

Index: ash/display/display_controller_unittest.cc
diff --git a/ash/display/display_controller_unittest.cc b/ash/display/display_controller_unittest.cc
index 273b461c56e4dd137536c2d1fe7c54da37bc8970..6b0407746807c23941a6cc8ab372e1b85958db4e 100644
--- a/ash/display/display_controller_unittest.cc
+++ b/ash/display/display_controller_unittest.cc
@@ -114,8 +114,10 @@ class TestObserver : public DisplayController::Observer,
   }
 
   // Overridden from aura::client::ActivationChangeObserver
-  void OnWindowActivated(aura::Window* gained_active,
-                         aura::Window* lost_active) override {
+  void OnWindowActivated(
+      aura::client::ActivationChangeObserver::ActivationReason reason,
+      aura::Window* gained_active,
+      aura::Window* lost_active) override {
     activation_changed_count_++;
   }
   void OnAttemptToReactivateWindow(aura::Window* request_active,