views: refactor away PlatformStyle::BackgroundColorForMdButton

ui/gfx/color_utils.h

Index: ui/gfx/color_utils.h
diff --git a/ui/gfx/color_utils.h b/ui/gfx/color_utils.h
index fc8b44652869e4d8c678aff83420c0db416f8f4e..1cc684080db4a325672cc3458414611e2fd23205 100644
--- a/ui/gfx/color_utils.h
+++ b/ui/gfx/color_utils.h
@@ -94,6 +94,10 @@ GFX_EXPORT double CalculateBoringScore(const SkBitmap& bitmap);
 GFX_EXPORT SkColor AlphaBlend(SkColor foreground, SkColor background,
                               SkAlpha alpha);
 
+// Returns the color that results from painting |foreground| on top of
+// |background|.
+GFX_EXPORT SkColor ImplicitAlphaBlend(SkColor foreground, SkColor background);
+
 // Returns true if the luma of |color| is closer to black than white.
 GFX_EXPORT bool IsDark(SkColor color);