Make LogoutButtonTray a regular View

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;
+
+// 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);
+  ~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_;
+
+  int main_axis_margin_ = 0;
+  int cross_axis_margin_ = 0;
+
+  DISALLOW_COPY_AND_ASSIGN(TrayContainer);
+};
+
+}  // namespace ash
+
+#endif  // ASH_SYSTEM_TRAY_TRAY_CONTAINER_H_