views: refactor away PlatformStyle::BackgroundColorForMdButton

ui/gfx/color_utils.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/gfx/color_utils.h"
 
 #include <stdint.h>
 
 #include <algorithm>
 #include <cmath>
@@ skipping 266 matching lines @@
               SkColorGetG(background) * b_weight) / 255.0;
   double b = (SkColorGetB(foreground) * f_weight +
               SkColorGetB(background) * b_weight) / 255.0;
 
   return SkColorSetARGB(static_cast<int>(std::round(normalizer)),
                         static_cast<int>(std::round(r)),
                         static_cast<int>(std::round(g)),
                         static_cast<int>(std::round(b)));
 }
 
+SkColor ImplicitAlphaBlend(SkColor foreground, SkColor background) {
+  return AlphaBlend(SkColorSetA(foreground, SK_AlphaOPAQUE), background,
+                    SkColorGetA(foreground));
+}
+
 bool IsDark(SkColor color) {
   return GetLuma(color) < 128;
 }
 
 SkColor BlendTowardOppositeLuma(SkColor color, SkAlpha alpha) {
   return AlphaBlend(IsDark(color) ? SK_ColorWHITE : SK_ColorBLACK, color,
                     alpha);
 }
 
 SkColor GetReadableColor(SkColor foreground, SkColor background) {
@@ skipping 39 matching lines @@
     // For black text, this comes out to kChromeIconGrey.
     return color_utils::AlphaBlend(SK_ColorWHITE, text_color,
                                    SkColorGetR(gfx::kChromeIconGrey));
   }
   // For a light color, just reduce opacity.
   return SkColorSetA(text_color,
                      static_cast<int>(0.8f * SkColorGetA(text_color)));
 }
 
 }  // namespace color_utils