mash: Partially migrate WorkspaceController to ash common.

ash/shelf/shelf_layout_manager.h

Index: ash/shelf/shelf_layout_manager.h
diff --git a/ash/shelf/shelf_layout_manager.h b/ash/shelf/shelf_layout_manager.h
index 934a08db2652e2c2ad4d44f5435e3a1fea33a0d0..4678bec86462cd7139e0345df72874799509350a 100644
--- a/ash/shelf/shelf_layout_manager.h
+++ b/ash/shelf/shelf_layout_manager.h
@@ -35,7 +35,6 @@ class PanelLayoutManagerTest;
 class ShelfLayoutManagerObserver;
 class ShelfLayoutManagerTest;
 class ShelfWidget;
-class WorkspaceController;
 
 // ShelfLayoutManager is the layout manager responsible for the shelf and
 // status widgets. The shelf is given the total available width and told the
@@ -56,10 +55,6 @@ class ASH_EXPORT ShelfLayoutManager
   explicit ShelfLayoutManager(ShelfWidget* shelf_widget);
   ~ShelfLayoutManager() override;
 
-  void set_workspace_controller(WorkspaceController* controller) {
-    workspace_controller_ = controller;
-  }
-
   bool updating_bounds() const { return updating_bounds_; }
 
   // Clears internal data for shutdown process.
@@ -311,8 +306,6 @@ class ASH_EXPORT ShelfLayoutManager
 
   ShelfWidget* shelf_widget_;
 
-  WorkspaceController* workspace_controller_;
-
   // Do any windows overlap the shelf? This is maintained by WorkspaceManager.
   bool window_overlaps_shelf_;