views: refactor away PlatformStyle::BackgroundColorForMdButton

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_utils.h"
@@ skipping 294 matching lines @@
     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);
   } else if (is_default()) {
     bg_color = color_utils::BlendTowardOppositeLuma(text_color, 0xD8);
   }
 
-  // TODO(ellyjones): Excise this, in favor of a helper function wrapping
-  // |color_utils::AlphaBlend| and a new NativeTheme color constant.
-  bg_color = PlatformStyle::BackgroundColorForMdButton(bg_color, state());
+  if (state() == STATE_PRESSED) {
+    SkColor shade =
+        theme->GetSystemColor(ui::NativeTheme::kColorId_ButtonPressedShade);
+    bg_color = color_utils::ImplicitAlphaBlend(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