MacViews: support backgrounds for selected rows

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 0d433480bfd1dfdca296d7a31376d3f7aaa44e19..125434971045848145dc052209c2985b4467b688 100644
--- a/ui/views/style/platform_style_mac.mm
+++ b/ui/views/style/platform_style_mac.mm
@@ -24,6 +24,7 @@ const int PlatformStyle::kMinLabelButtonHeight = 30;
 const bool PlatformStyle::kDefaultLabelButtonHasBoldFont = false;
 const bool PlatformStyle::kDialogDefaultButtonCanBeCancel = false;
 const bool PlatformStyle::kTextfieldDragVerticallyDragsToEnd = true;
+const bool PlatformStyle::kTreeViewSelectionPaintsEntireRow = true;
 
 const CustomButton::NotifyAction PlatformStyle::kMenuNotifyActivationAction =
     CustomButton::NOTIFY_ON_PRESS;