mash: Replace ShelfItemDelegate::CanPin with ShelfItem::pinned_by_policy.

ash/shell/window_watcher_shelf_item_delegate.cc

 // Copyright 2013 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.
 
 #include "ash/shell/window_watcher_shelf_item_delegate.h"
 
 #include "ash/shell/window_watcher.h"
 #include "ash/wm/window_util.h"
 #include "ui/aura/window.h"
 
@@ skipping 22 matching lines @@
 
 base::string16 WindowWatcherShelfItemDelegate::GetTitle() {
   return watcher_->GetWindowByID(id_)->GetTitle();
 }
 
 ShelfMenuModel* WindowWatcherShelfItemDelegate::CreateApplicationMenu(
     int event_flags) {
   return nullptr;
 }
 
-bool WindowWatcherShelfItemDelegate::CanPin() const {
-  return true;
-}
-
 void WindowWatcherShelfItemDelegate::Close() {}
 
 }  // namespace shell
 }  // namespace ash