Position close buttons in bubbles based on a layout delegate constant.

ui/views/layout/layout_constants.h

 // 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.
 
 #ifndef UI_VIEWS_LAYOUT_LAYOUT_CONSTANTS_H_
 #define UI_VIEWS_LAYOUT_LAYOUT_CONSTANTS_H_
 
 #include "build/build_config.h"
 #include "ui/views/layout/grid_layout.h"
 
@@ skipping 52 matching lines @@
 constexpr int kButtonHEdgeMargin = 13;
 
 // Vertical spacing between the edge of the window and the
 // top or bottom of a button (when using new style dialogs).
 constexpr int kButtonVEdgeMarginNew = 20;
 
 // Horizontal spacing between the edge of the window and the
 // left or right of a button (when using new style dialogs).
 constexpr int kButtonHEdgeMarginNew = 20;
 
+// Spacing between the edge of the window and the edge of the close button.
+const int kCloseButtonMargin = 7;
+
 // Horizontal spacing between buttons that are logically related.
 constexpr int kRelatedButtonHSpacing = 6;
 
 // Indent of checkboxes relative to related text.
 constexpr int kCheckboxIndent = 10;
 
 // Horizontal spacing between the end of an item (i.e. an icon or a checkbox)
 // and the start of its corresponding text.
 constexpr int kItemLabelSpacing = 10;
 
 }  // namespace views
 
 #endif  // UI_VIEWS_LAYOUT_LAYOUT_CONSTANTS_H_