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

ash/shelf/shelf_layout_manager.cc

Index: ash/shelf/shelf_layout_manager.cc
diff --git a/ash/shelf/shelf_layout_manager.cc b/ash/shelf/shelf_layout_manager.cc
index e41b3490ba6a188096d78a765f3f52c5d025b095..75e273b3cd6118af3531735fe5536f263d47734c 100644
--- a/ash/shelf/shelf_layout_manager.cc
+++ b/ash/shelf/shelf_layout_manager.cc
@@ -529,8 +529,10 @@ void ShelfLayoutManager::OnLockStateChanged(bool locked) {
   UpdateShelfVisibilityAfterLoginUIChange();
 }
 
-void ShelfLayoutManager::OnWindowActivated(aura::Window* gained_active,
-                                           aura::Window* lost_active) {
+void ShelfLayoutManager::OnWindowActivated(
+    aura::client::ActivationChangeObserver::ActivationReason reason,
+    aura::Window* gained_active,
+    aura::Window* lost_active) {
   UpdateAutoHideStateNow();
 }