Pass shelf instances, not root windows, for ash context menus.

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index 6949d6c049454479fdf10c2f4a173303eecaf4dc..71231a211d76645bb7a99960228374eda8f10a10 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -523,17 +523,19 @@ ShelfAutoHideBehavior Shell::GetShelfAutoHideBehavior(
 void Shell::SetShelfAlignment(ShelfAlignment alignment,
                               aura::Window* root_window) {
   ShelfWidget* shelf_widget = GetRootWindowController(root_window)->shelf();
-  if (shelf_widget->shelf_layout_manager()->SetAlignment(alignment)) {
-    FOR_EACH_OBSERVER(
-        ShellObserver, observers_, OnShelfAlignmentChanged(root_window));
-  }
+  shelf_widget->shelf_layout_manager()->SetAlignment(alignment);
 }
 
-ShelfAlignment Shell::GetShelfAlignment(const aura::Window* root_window) {
+ShelfAlignment Shell::GetShelfAlignment(const aura::Window* root_window) const {
   ShelfWidget* shelf_widget = GetRootWindowController(root_window)->shelf();
   return shelf_widget->shelf_layout_manager()->GetAlignment();
 }
 
+void Shell::OnShelfAlignmentChanged(aura::Window* root_window) {
+  FOR_EACH_OBSERVER(ShellObserver, observers_,
+                    OnShelfAlignmentChanged(root_window));
+}
+
 void Shell::NotifyFullscreenStateChange(bool is_fullscreen,
                                         aura::Window* root_window) {
   FOR_EACH_OBSERVER(ShellObserver, observers_, OnFullscreenStateChanged(