mash: Move tray_constants.h and FixedSizedImageView to //ash/common

ash/system/tray/fixed_sized_image_view.h

-// 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.
-
-#ifndef ASH_SYSTEM_TRAY_FIXED_SIZED_IMAGE_VIEW_H_
-#define ASH_SYSTEM_TRAY_FIXED_SIZED_IMAGE_VIEW_H_
-
-#include "base/compiler_specific.h"
-#include "base/macros.h"
-#include "ui/views/controls/image_view.h"
-
-namespace ash {
-
-// An image view with a specified width and height (kTrayPopupDetailsIconWidth).
-// If the specified width or height is zero, then the image size is used for
-// that dimension.
-class FixedSizedImageView : public views::ImageView {
- public:
-  FixedSizedImageView(int width, int height);
-  ~FixedSizedImageView() override;
-
- private:
-  gfx::Size GetPreferredSize() const override;
-
-  int width_;
-  int height_;
-
-  DISALLOW_COPY_AND_ASSIGN(FixedSizedImageView);
-};
-
-}  // namespace ash
-
-#endif  // ASH_SYSTEM_TRAY_FIXED_SIZED_IMAGE_VIEW_H_