Move common notification layout to base class

ash/system/tray/tray_constants.cc

 // Copyright (c) 2012 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_constants.h"
 
 #include "third_party/skia/include/core/SkColor.h"
 
 namespace ash {
 
@@ skipping 22 matching lines @@
 const SkColor kBorderDarkColor = SkColorSetRGB(0xbb, 0xbb, 0xbb);
 const SkColor kBorderLightColor = SkColorSetRGB(0xeb, 0xeb, 0xeb);
 const SkColor kButtonStrokeColor = SkColorSetRGB(0xdd, 0xdd, 0xdd);
 
 const SkColor kFocusBorderColor = SkColorSetRGB(64, 128, 250);
 
 const SkColor kHeaderTextColorNormal = SkColorSetARGB(0x7f, 0, 0, 0);
 const SkColor kHeaderTextColorHover = SkColorSetARGB(0xd3, 0, 0, 0);
 
 const int kTrayPopupWidth = 300;
-const int kNotificationCloseButtonWidth = 60;
 const int kNotificationIconWidth = 40;
+const int kTrayNotificationContentsWidth =
+    kTrayPopupWidth - kNotificationIconWidth*2 - kTrayPopupPaddingHorizontal*2;
 
 }  // namespace ash