Add WindowPinType property on arua::Window

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 398ea45f1f2b2f62250d57333d5d0e4cbb22895b..34f5d084022f05a97e01b489365dc3510452168f 100644
--- a/ui/views/widget/native_widget_mac.mm
+++ b/ui/views/widget/native_widget_mac.mm
@@ -510,6 +510,16 @@ bool NativeWidgetMac::IsFullscreen() const {
   return bridge_ && bridge_->target_fullscreen_state();
 }
 
+void NativeWidgetMac::Pin(bool trusted) {
+  // We only use Pin() for ARC++ window on Chromebook, so we don't need
+  // implement it for Mac.
+  NOTIMPLEMENTED();
+}
+
+bool NativeWidgetMac::IsPinned() const {
+  return false;
+}
+
 void NativeWidgetMac::SetOpacity(float opacity) {
   [GetNativeWindow() setAlphaValue:opacity];
 }