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 2570d3ec94721a0e61f1244e7de9fdb93dfcb5e0..d664965829646331e4b673b4a974e0f2dda60cc4 100644
--- a/ash/wm/workspace/workspace_layout_manager_unittest.cc
+++ b/ash/wm/workspace/workspace_layout_manager_unittest.cc
@@ -883,7 +883,8 @@ 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));