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

ui/views/controls/button/md_text_button.cc

 // 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.
 
 #include "ui/views/controls/button/md_text_button.h"
 
 #include "base/i18n/case_conversion.h"
 #include "ui/base/material_design/material_design_controller.h"
 #include "ui/gfx/canvas.h"
+#include "ui/gfx/color_palette.h"
 #include "ui/gfx/color_utils.h"
 #include "ui/native_theme/native_theme.h"
 #include "ui/views/animation/flood_fill_ink_drop_ripple.h"
 #include "ui/views/animation/ink_drop_highlight.h"
 #include "ui/views/animation/ink_drop_painted_layer_delegates.h"
 #include "ui/views/background.h"
 #include "ui/views/border.h"
 #include "ui/views/controls/button/blue_button.h"
 #include "ui/views/painter.h"
 #include "ui/views/style/platform_style.h"
@@ skipping 280 matching lines @@
   SkColor text_color = label()->enabled_color();
   SkColor bg_color =
       theme->GetSystemColor(ui::NativeTheme::kColorId_DialogBackground);
 
   if (bg_color_override_) {
     bg_color = *bg_color_override_;
   } else if (is_cta_) {
     bg_color = theme->GetSystemColor(
         ui::NativeTheme::kColorId_CallToActionColor);
     if (state() == STATE_DISABLED)
-      bg_color = color_utils::BlendTowardOppositeLuma(bg_color, 0x61);
+      bg_color = color_utils::BlendTowardOppositeLuma(
+          bg_color, gfx::kDisabledControlAlpha);
   } else if (is_default()) {
     bg_color = color_utils::BlendTowardOppositeLuma(text_color, 0xD8);
   }
 
   if (state() == STATE_PRESSED) {
     SkColor shade =
         theme->GetSystemColor(ui::NativeTheme::kColorId_ButtonPressedShade);
     bg_color = color_utils::GetResultingPaintColor(shade, bg_color);
   }
 
   const SkAlpha kStrokeOpacity = 0x1A;
   SkColor stroke_color = (is_cta_ || color_utils::IsDark(text_color))
                              ? SkColorSetA(SK_ColorBLACK, kStrokeOpacity)
                              : SkColorSetA(SK_ColorWHITE, 2 * kStrokeOpacity);
 
   DCHECK_EQ(SK_AlphaOPAQUE, static_cast<int>(SkColorGetA(bg_color)));
   set_background(Background::CreateBackgroundPainter(
       true, Painter::CreateRoundRectWith1PxBorderPainter(
                 bg_color, stroke_color, kInkDropSmallCornerRadius)));
 }
 
 }  // namespace views