Solved the bug related to the toggle inspector of iOS

Summary:
Before this diff the nodes were not invalidated properly when the new view got added in the hierarchy, due to this there was following bug.

https://our.intern.facebook.com/intern/px/p/15RSP

Reviewed By: Andrey-Mishanin

Differential Revision: D21285438

fbshipit-source-id: b72aa93856688b31296ae1df4f15e128037aa1ca

iOS/Plugins/FlipperKitLayoutPlugin/FlipperKitLayoutPlugin/FlipperKitLayoutPlugin.mm

@@ -371,6 +371,10 @@
       });
 }
 
+- (void)invalidateRootNode {
+  [self invalidateNode:_rootNode];
+}
+
 - (void)_reportInvalidatedObjects {
   NSMutableArray* nodes = [NSMutableArray new];
   { // scope mutex acquisition

iOS/Plugins/FlipperKitLayoutPlugin/FlipperKitLayoutPlugin/SKInvalidation.h

@@ -10,7 +10,7 @@
 @protocol SKInvalidationDelegate
 
 - (void)invalidateNode:(id<NSObject>)node;
-
+- (void)invalidateRootNode;
 - (void)updateNodeReference:(id<NSObject>)node;
 
 @end

iOS/Plugins/FlipperKitLayoutPlugin/FlipperKitLayoutPlugin/UIView+SKInvalidation.mm

@@ -9,7 +9,6 @@
 
 #import <UIKit/UIKit.h>
 #import <objc/runtime.h>
-
 #import "SKInvalidation.h"
 #import "SKSwizzle.h"
 #import "UIView+SKInvalidation.h"
@@ -31,6 +30,14 @@ FB_LINKABLE(UIView_SKInvalidation)
   });
 }
 
+/**
+This function takes in a view and returns true if the view is a UIWindow and its
+windowLevel is an alert one otherwise it returns false.
+*/
+static auto shouldInvalidateRootNode(UIView* view) -> bool {
+  return [view isKindOfClass:[UIWindow class]];
+}
+
 - (void)swizzle_setHidden:(BOOL)hidden {
   [self swizzle_setHidden:hidden];
 
@@ -47,7 +54,11 @@ FB_LINKABLE(UIView_SKInvalidation)
   id<SKInvalidationDelegate> delegate =
       [SKInvalidation sharedInstance].delegate;
   if (delegate != nil) {
-    [delegate invalidateNode:view];
+    if (shouldInvalidateRootNode(view.superview)) {
+      [delegate invalidateRootNode];
+      return;
+    }
+    [delegate invalidateNode:view.superview];
   }
 }
 
@@ -55,6 +66,10 @@ FB_LINKABLE(UIView_SKInvalidation)
   id<SKInvalidationDelegate> delegate =
       [SKInvalidation sharedInstance].delegate;
   if (delegate != nil && self.superview != nil) {
+    if (shouldInvalidateRootNode(self.superview)) {
+      [delegate invalidateRootNode];
+      return;
+    }
     [delegate invalidateNode:self.superview];
   }