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

ash/system/tray/tray_popup_header_button.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/system/tray/tray_popup_header_button.h"
 
 #include "ash/ash_constants.h"
-#include "ash/system/tray/tray_constants.h"
+#include "ash/common/system/tray/tray_constants.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/views/background.h"
 #include "ui/views/painter.h"
 
 namespace ash {
 
 // static
 const char TrayPopupHeaderButton::kViewClassName[] =
     "tray/TrayPopupHeaderButton";
 
@@ skipping 37 matching lines @@
   if (state() == STATE_HOVERED || state() == STATE_PRESSED) {
     set_background(views::Background::CreateSolidBackground(
         kTrayPopupHoverBackgroundColor));
   } else {
     set_background(nullptr);
   }
   SchedulePaint();
 }
 
 }  // namespace ash