Refactor backdrop that is currently used in the maximized mode.

ash/ash_touch_exploration_manager_chromeos.cc

Index: ash/ash_touch_exploration_manager_chromeos.cc
diff --git a/ash/ash_touch_exploration_manager_chromeos.cc b/ash/ash_touch_exploration_manager_chromeos.cc
index c9ed8ac41cc1bfc801928343b082113e9702c0ca..6120ffbf4de19d4c49fe0ea4118585cf05818dad 100644
--- a/ash/ash_touch_exploration_manager_chromeos.cc
+++ b/ash/ash_touch_exploration_manager_chromeos.cc
@@ -167,9 +167,9 @@ void AshTouchExplorationManager::UpdateTouchExplorationState() {
               touch_accessibility_enabler_.get());
     }
     if (pass_through_surface) {
-      const gfx::Rect& work_area = root_window_controller_->GetWindow()
-                                       ->GetDisplayNearestWindow()
-                                       .work_area();
+      const gfx::Rect work_area = root_window_controller_->GetWindow()
+                                      ->GetDisplayNearestWindow()
+                                      .work_area();
       touch_exploration_controller_->SetExcludeBounds(work_area);
       SilenceSpokenFeedback();
       Shell::Get()->accessibility_delegate()->ClearFocusHighlight();