add macOS descriptors for layout plugin

Summary: Add macOS only descriptors. Currently does not support Yoga/YogaKit or accessibility features; will add those in a later diff.

Reviewed By: priteshrnandgaonkar

Differential Revision: D27332601

fbshipit-source-id: 35c93cf715f004dbf8dbf8753534f1d4f9801b4c

iOS/Plugins/FlipperKitLayoutPlugin/FlipperKitLayoutPlugin/FlipperKitLayoutPlugin.mm

@@ -70,8 +70,12 @@ NSObject* flattenLayoutEditorMessage(NSObject* field);
   _connection = connection;
 
   if (!_rootNode) {
-    // TODO: T61384369 get rid off this if condition.
+// TODO: T61384369 get rid off this if condition.
+#if TARGET_OS_IPHONE
     _rootNode = [UIApplication sharedApplication];
+#elif TARGET_OS_OSX
+    _rootNode = [NSApplication sharedApplication];
+#endif
   }
 
   [SKInvalidation enableInvalidations];
@@ -366,7 +370,11 @@ NSObject* flattenLayoutEditorMessage(NSObject* field) {
 - (void)onCallSetSearchActive:(BOOL)active
                withConnection:(id<FlipperConnection>)connection {
   if (active) {
+#if TARGET_OS_IPHONE
     [_tapListener mountWithFrame:[[UIScreen mainScreen] bounds]];
+#elif TARGET_OS_OSX
+    [_tapListener mountWithFrame:NSRectToCGRect([NSScreen mainScreen].frame)];
+#endif
     __block id<NSObject> rootNode = _rootNode;
 
     [_tapListener listenForTapWithBlock:^(CGPoint touchPoint) {