MacViews: draw Mac combobox arrows

ui/views/style/platform_style_mac.mm

Index: ui/views/style/platform_style_mac.mm
diff --git a/ui/views/style/platform_style_mac.mm b/ui/views/style/platform_style_mac.mm
index 1fb13f32a554ed486c3021b84e7bd534ac77104f..a0d0c5776f09705180a0ea58d4db233e04cb6e66 100644
--- a/ui/views/style/platform_style_mac.mm
+++ b/ui/views/style/platform_style_mac.mm
@@ -4,6 +4,8 @@
 
 #include "ui/views/style/platform_style.h"
 
+#include "ui/gfx/paint_vector_icon.h"
+#include "ui/gfx/vector_icons.h"
 #include "ui/views/controls/button/label_button.h"
 #include "ui/views/controls/button/label_button_border.h"
 #include "ui/views/controls/focusable_rounded_border_mac.h"
@@ -14,6 +16,14 @@
 namespace views {
 
 // static
+gfx::ImageSkia PlatformStyle::CreateComboboxArrow(bool is_enabled) {
+  const int kComboboxArrowWidth = 13;
+  return gfx::CreateVectorIcon(gfx::VectorIconId::COMBOBOX_ARROW_MAC,
+                               kComboboxArrowWidth,
+                               is_enabled ? SK_ColorWHITE : SK_ColorBLACK);
+}
+
+// static
 scoped_ptr<FocusableBorder> PlatformStyle::CreateComboboxBorder() {
   return make_scoped_ptr(new FocusableRoundedBorder);
 }