Adds a test that verifies that navigating in the unload handler while

content/renderer/render_frame_impl.cc

Index: content/renderer/render_frame_impl.cc
diff --git a/content/renderer/render_frame_impl.cc b/content/renderer/render_frame_impl.cc
index 6c4675a18a59a0d9e09809eb1af7b6d5deb61f7f..1c8e004f162b0cbd28cf09a7c4fe420f48eac35c 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -1686,8 +1686,6 @@ void RenderFrameImpl::OnSwapOut(
     // The swap can fail when the frame is detached during swap (this can
     // happen while running the unload handlers). When that happens, delete
     // the proxy.
-    // TODO(lfg): Handle the case where a navigation started during swap.
-    // See https://crbug.com/590054 for more details.
     proxy->frameDetached(blink::WebRemoteFrameClient::DetachType::Swap);
     return;
   }