chromeos: Rename ash::WmShelf to Shelf

ash/system/tray/tray_container.h

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_SYSTEM_TRAY_TRAY_CONTAINER_H_
 #define ASH_SYSTEM_TRAY_TRAY_CONTAINER_H_
 
 #include "base/macros.h"
 #include "ui/views/view.h"
 
 namespace ash {
-class WmShelf;
+class Shelf;
 
 // Base class for tray containers. Sets the border and layout. The container
 // auto-resizes the widget when necessary.
 class TrayContainer : public views::View {
  public:
-  explicit TrayContainer(WmShelf* wm_shelf);
+  explicit TrayContainer(Shelf* shelf);
   ~TrayContainer() override;
 
   void UpdateAfterShelfAlignmentChange();
 
   void SetMargin(int main_axis_margin, int cross_axis_margin);
 
  protected:
   // views::View:
   void ChildPreferredSizeChanged(views::View* child) override;
   void ChildVisibilityChanged(View* child) override;
   void ViewHierarchyChanged(
       const ViewHierarchyChangedDetails& details) override;
 
  private:
   void UpdateLayout();
 
-  WmShelf* const wm_shelf_;
+  Shelf* const shelf_;
 
   int main_axis_margin_ = 0;
   int cross_axis_margin_ = 0;
 
   DISALLOW_COPY_AND_ASSIGN(TrayContainer);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_TRAY_CONTAINER_H_