Moves a couple of the maximize mode classes to ash/common

ash/wm/workspace/workspace_layout_manager_unittest.cc

Index: ash/wm/workspace/workspace_layout_manager_unittest.cc
diff --git a/ash/wm/workspace/workspace_layout_manager_unittest.cc b/ash/wm/workspace/workspace_layout_manager_unittest.cc
index 4f8acd3af5e43a00fcad7ece3eadc31194ee3f13..cbbe7789761a470866da2fe0f90e3ab63fdd61b0 100644
--- a/ash/wm/workspace/workspace_layout_manager_unittest.cc
+++ b/ash/wm/workspace/workspace_layout_manager_unittest.cc
@@ -892,7 +892,8 @@ class WorkspaceLayoutManagerBackdropTest : public test::AshTestBase {
   void ShowTopWindowBackdrop(bool show) {
     std::unique_ptr<ash::WorkspaceLayoutManagerBackdropDelegate> backdrop;
     if (show) {
-      backdrop.reset(new ash::WorkspaceBackdropDelegate(default_container_));
+      backdrop.reset(new ash::WorkspaceBackdropDelegate(
+          WmWindowAura::Get(default_container_)));
     }
     GetWorkspaceLayoutManager(default_container_)
         ->SetMaximizeBackdropDelegate(std::move(backdrop));