[MacViews] Use NSTitledWindowMask for window modal dialogs.

ui/views/widget/native_widget_mac.mm

Index: ui/views/widget/native_widget_mac.mm
diff --git a/ui/views/widget/native_widget_mac.mm b/ui/views/widget/native_widget_mac.mm
index c5546ea187898ce84721791b8be94accbd550ab0..067e9ea461b1fc4574c82dda9b701b4ac6bcba77 100644
--- a/ui/views/widget/native_widget_mac.mm
+++ b/ui/views/widget/native_widget_mac.mm
@@ -38,6 +38,11 @@ namespace views {
 namespace {
 
 NSInteger StyleMaskForParams(const Widget::InitParams& params) {
+  // If the widget is modal, it will be displayed as a sheet. This only works

[tapted, 2015/08/19 09:02:14]

nit: widget -> Widget
(and perhaps "only works" -> "works best")

[jackhou1, 2015/08/20 00:01:36]

Done.

+  // if it has NSTitledWindowMask.

[tapted, 2015/08/19 09:02:14]

nit: perhaps worth adding "(e.g. with NSBorderlessWindowMask. the parent window
still accepts input)."

[jackhou1, 2015/08/20 00:01:36]

Done.

+  if (params.delegate->GetModalType() == ui::MODAL_TYPE_WINDOW)

[tapted, 2015/08/19 09:02:14]

params.delegate && ... 

(params.delegate can be null)

[jackhou1, 2015/08/20 00:01:36]

Done.

+    return NSTitledWindowMask;
+
   // TODO(tapted): Determine better masks when there are use cases for it.
   if (params.remove_standard_frame)
     return NSBorderlessWindowMask;