MacViews: Use the Aura color for prominent button backgrounds.

ui/native_theme/native_theme_mac.mm

Index: ui/native_theme/native_theme_mac.mm
diff --git a/ui/native_theme/native_theme_mac.mm b/ui/native_theme/native_theme_mac.mm
index 5b46fbb44f658c1c242c51ad53c565bee67b820f..a88fafc9fc404c36898cbcb08279b01f01c71d01 100644
--- a/ui/native_theme/native_theme_mac.mm
+++ b/ui/native_theme/native_theme_mac.mm
@@ -181,8 +181,12 @@ SkColor NativeThemeMac::GetSystemColor(ColorId color_id) const {
     // Buttons and labels.
     case kColorId_ButtonEnabledColor:
     case kColorId_LabelEnabledColor:
-    case kColorId_ProminentButtonColor:
       return NSSystemColorToSkColor([NSColor controlTextColor]);
+    // NSColor doesn't offer a color for prominent buttons. Use the Aura color,
+    // but apply the system tint. This is a good match for the blue Cocoa uses
+    // to draw buttons that are given a \n key equivalent.
+    case kColorId_ProminentButtonColor:
+      return ApplySystemControlTint(GetAuraColor(color_id, this));
     case kColorId_ButtonDisabledColor:
     case kColorId_LabelDisabledColor:
       return NSSystemColorToSkColor([NSColor disabledControlTextColor]);