Share a common alpha value used for displaying disabled state in Harmony

ui/views/controls/combobox/combobox.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 "ui/views/controls/combobox/combobox.h"
 
 #include <stddef.h>
 
 #include <utility>
 
@@ skipping 815 matching lines @@
     // slightly less than half full and come out a little lighter.
     const SkScalar kEpsilon = 0.0001f;
     path.moveTo(x - kEpsilon, y);
     path.rLineTo(height, height);
     path.rLineTo(2 * kEpsilon, 0);
     path.rLineTo(height, -height);
     path.close();
     SkPaint paint;
     SkColor arrow_color = GetNativeTheme()->GetSystemColor(
         ui::NativeTheme::kColorId_ButtonEnabledColor);
-    // TODO(estade): share this disabled alpha value with other places that use
-    // it.
     if (!enabled())
-      arrow_color = SkColorSetA(arrow_color, 0x61);
+      arrow_color = SkColorSetA(arrow_color, gfx::kDisabledControlAlpha);
     paint.setColor(arrow_color);
     paint.setAntiAlias(true);
     canvas->DrawPath(path, paint);
   } else {
     canvas->DrawImageInt(arrow_image_, arrow_bounds.x(), arrow_bounds.y());
   }
 }
 
 void Combobox::PaintButtons(gfx::Canvas* canvas) {
   DCHECK(style_ == STYLE_ACTION);
@@ skipping 139 matching lines @@
 }
 
 int Combobox::GetArrowContainerWidth() const {
   int padding = style_ == STYLE_NORMAL
                     ? PlatformStyle::kComboboxNormalArrowPadding * 2
                     : kActionLeftPadding + kActionRightPadding;
   return ArrowSize().width() + padding;
 }
 
 }  // namespace views