Wires up shelf to panel and dock layoutmanagers

mash/wm/shelf_layout_manager_delegate.h

+// Copyright 2016 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 MASH_WM_SHELF_LAYOUT_MANAGER_DELEGATE_H_
+#define MASH_WM_SHELF_LAYOUT_MANAGER_DELEGATE_H_
+
+namespace mash {
+namespace wm {
+
+class ShelfLayoutManagerDelegate {
+ public:
+  // Called when the window associated with the shelf is available. That is,
+  // ShelfLayoutManager::GetShelfWindow() returns non-null.
+  virtual void OnShelfWindowAvailable() = 0;
+
+ protected:
+  virtual ~ShelfLayoutManagerDelegate() {}
+};
+
+}  // namespace wm
+}  // namespace mash
+
+#endif  // MASH_WM_SHELF_LAYOUT_MANAGER_DELEGATE_H_