Add initial decor view traversal

Summary: Catch the case when we mis the initial draw

Reviewed By: lblasa

Differential Revision: D39658946

fbshipit-source-id: 00a46226128e28a8753df2161d1edcd6ffa47d67

android/src/main/java/com/facebook/flipper/plugins/uidebugger/observers/DecorViewTreeObserver.kt

@@ -49,6 +49,8 @@ class DecorViewObserver(val context: Context) : TreeObserver<DecorView>() {
         }
 
     node.viewTreeObserver.addOnPreDrawListener(listener)
+    // sometimes we are too late to the party and we miss the first draw
+    listener?.onPreDraw()
   }
 
   override fun unsubscribe() {