Refined DCHECK preventing multiple event forwarders in VA tree path

ui/android/view_android_unittests.cc

Index: ui/android/view_android_unittests.cc
diff --git a/ui/android/view_android_unittests.cc b/ui/android/view_android_unittests.cc
index 77c9bcae16534428660684bb80c2c99af788a641..e21c2918f1f5f48cc1162d32048c2e712652582c 100644
--- a/ui/android/view_android_unittests.cc
+++ b/ui/android/view_android_unittests.cc
@@ -6,6 +6,7 @@
 #include "ui/android/event_forwarder.h"
 #include "ui/android/view_android.h"
 #include "ui/android/view_client.h"
+#include "ui/android/window_android.h"
 #include "ui/events/android/motion_event_android.h"
 
 namespace ui {
@@ -166,4 +167,18 @@ TEST_F(ViewAndroidBoundsTest, MatchesViewsWithOffset) {
   ExpectHit(client3_);
 }
 
+TEST(ViewAndroidTest, AddChildChecksMultipleEventForwarders) {
+  ViewAndroid view1;
+  ViewAndroid view2;
+  view1.GetEventForwarder();
+  view2.GetEventForwarder();
+  EXPECT_DEATH(view1.AddChild(&view2), "Check failed:");
+
+  WindowAndroid* window = WindowAndroid::CreateForTesting();
+  view2.RemoveFromParent();
+  window->AddChild(&view1);
+  window->AddChild(&view2);
+  window->Destroy(nullptr, nullptr);
+}
+
 }  // namespace ui