mash: Remove WorkspaceLayoutManagerDelegate.

ash/common/wm/workspace/workspace_layout_manager.h

Index: ash/common/wm/workspace/workspace_layout_manager.h
diff --git a/ash/common/wm/workspace/workspace_layout_manager.h b/ash/common/wm/workspace/workspace_layout_manager.h
index a91fc6156a892b3f2e40c87fe6284d7ca66805ca..19e47be92df464c818c63ccc9ee05dff30ef9bb5 100644
--- a/ash/common/wm/workspace/workspace_layout_manager.h
+++ b/ash/common/wm/workspace/workspace_layout_manager.h
@@ -26,7 +26,6 @@ class WmRootWindowController;
 class WorkspaceLayoutManagerBackdropDelegate;
 
 namespace wm {
-class WorkspaceLayoutManagerDelegate;
 class WMEvent;
 }
 
@@ -40,14 +39,9 @@ class ASH_EXPORT WorkspaceLayoutManager
       public ShellObserver,
       public wm::WindowStateObserver {
  public:
-  WorkspaceLayoutManager(
-      WmWindow* window,
-      std::unique_ptr<wm::WorkspaceLayoutManagerDelegate> delegate);
-
+  explicit WorkspaceLayoutManager(WmWindow* window);
   ~WorkspaceLayoutManager() override;
 
-  void DeleteDelegate();
-
   // A delegate which can be set to add a backdrop behind the top most visible
   // window. With the call the ownership of the delegate will be transferred to
   // the WorkspaceLayoutManager.
@@ -127,8 +121,6 @@ class ASH_EXPORT WorkspaceLayoutManager
   WmRootWindowController* root_window_controller_;
   WmShell* shell_;
 
-  std::unique_ptr<wm::WorkspaceLayoutManagerDelegate> delegate_;
-
   // Set of windows we're listening to.
   WindowSet windows_;