views: support disabled color for CTA buttons

ui/native_theme/common_theme.cc

Index: ui/native_theme/common_theme.cc
diff --git a/ui/native_theme/common_theme.cc b/ui/native_theme/common_theme.cc
index 78c5b5bffe3ca5a90f53b3f5e931983a6ecf2e21..1b8b1d9ef081891a6c79642d16d39988a11b9d9d 100644
--- a/ui/native_theme/common_theme.cc
+++ b/ui/native_theme/common_theme.cc
@@ -137,6 +137,8 @@ SkColor GetAuraColor(NativeTheme::ColorId color_id,
   static const SkColor kBlueButtonHoverColor = SK_ColorWHITE;
   static const SkColor kBlueButtonShadowColor = SkColorSetRGB(0x53, 0x8C, 0xEA);
   static const SkColor kCallToActionColor = gfx::kGoogleBlue500;
+  static const SkColor kCallToActionDisabledColor =
+      SkColorSetA(kCallToActionColor, 255.0 * 0.38);
   static const SkColor kTextOnCallToActionColor = SK_ColorWHITE;
   // MenuItem:
   static const SkColor kMenuBackgroundColor = SK_ColorWHITE;
@@ -272,6 +274,8 @@ SkColor GetAuraColor(NativeTheme::ColorId color_id,
       return kBlueButtonShadowColor;
     case NativeTheme::kColorId_CallToActionColor:
       return kCallToActionColor;
+    case NativeTheme::kColorId_CallToActionDisabledColor:
+      return kCallToActionDisabledColor;
     case NativeTheme::kColorId_TextOnCallToActionColor:
       return kTextOnCallToActionColor;