Don't simulate UnloadACK on frames that are not live.

Unload is not called on frames if they are not live.

https://source.chromium.org/chromium/chromium/src/+/master:content/browser/renderer_host/render_frame_host_manager.cc;l=481;drc=420adc39b2caf85261a08935ec47c03745100e1f

Bug: 1072817
Change-Id: I5e00d678cf1bd80d928b3fb3ade292741eff9a1e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2410099
Commit-Queue: Fergal Daly <fergal@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#807382}

content/test/navigation_simulator_impl.cc

@@ -1399,6 +1399,10 @@ void NavigationSimulatorImpl::
     return;
   if (drop_unload_ack_)
     return;
+  // The previous RenderFrameHost is not live, we will not attempt to unload
+  // it.
+  if (!previous_rfh->IsRenderFrameLive())
+    return;
   // The previous RenderFrameHost entered the back-forward cache and hasn't been
   // requested to unload. The browser process do not expect
   // FrameHostMsg_Unload_ACK.