Do not use assets for Ash window control button backgrounds

ash/ash_layout_constants.h

Index: ash/ash_layout_constants.h
diff --git a/ash/ash_layout_constants.h b/ash/ash_layout_constants.h
new file mode 100644
index 0000000000000000000000000000000000000000..d2a17e171fb690a553c7364c2cc6259624459f4f
--- /dev/null
+++ b/ash/ash_layout_constants.h
@@ -0,0 +1,23 @@
+// Copyright 2015 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_ASH_LAYOUT_CONSTANTS_H_
+#define ASH_ASH_LAYOUT_CONSTANTS_H_
+
+#include "ui/gfx/geometry/size.h"
+
+enum AshLayoutSize {
+  // Size of a header button in a maximized browser window.

[Peter Kasting, 2015/12/18 18:59:15]

At least on Windows, these are called "caption buttons".  Unless Ash
consistently refers to them as "header buttons", I'd use that terminology
everywhere.

[tdanderson, 2016/01/04 23:11:14]

Done.

+  BROWSER_MAXIMIZED_HEADER_BUTTON,
+
+  // Size of a header button in a restored browser window.
+  BROWSER_RESTORED_HEADER_BUTTON,
+
+  // Size of a header button in a non-browser window.
+  DEFAULT_HEADER_BUTTON,

[Peter Kasting, 2015/12/18 18:59:15]

Nit: I might name this "NON_BROWSER_" instead of "DEFAULT_" since browser
windows are much more common than non-browser windows, and it's kinda weird to
have "default" for the minority case.

[tdanderson, 2016/01/04 23:11:14]

Done.

+};
+
+gfx::Size GetAshLayoutSize(AshLayoutSize size);
+
+#endif  // ASH_ASH_LAYOUT_CONSTANTS_H_