Revert performance monitor change (#36)

Author: alanjhughes

packages/react-native/React/CoreModules/RCTPerfMonitor.mm

@@ -297,7 +297,11 @@ - (void)show
 
   [self updateStats];
 
-  [RCTKeyWindow() addSubview:self.container];
+  // This change is causing the performance monitor and element inspector to be added to the dev menus UIWindow
+  // instead of the main app
+  // [RCTKeyWindow() addSubview:self.container];
+  UIWindow *window = RCTSharedApplication().delegate.window;
+  [window addSubview:self.container];
 
   _uiDisplayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(threadUpdate:)];
   [_uiDisplayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];