RemoteMacViews: Close window on process exit

Process death should be treated as window exit. Tested using a process
kill.

Bug: 898627
Change-Id: I4e659dfeb71541ac2e111979842eda40110d7a66
Reviewed-on: https://chromium-review.googlesource.com/c/1298297Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: ccameron <ccameron@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602473}

ui/views/cocoa/bridged_native_widget_host_impl.mm

@@ -493,7 +493,17 @@ void BridgedNativeWidgetHostImpl::OnBridgeFactoryHostDestroying(
   DCHECK_EQ(host, bridge_factory_host_);
   bridge_factory_host_->RemoveObserver(this);
   bridge_factory_host_ = nullptr;
-  // TODO(ccameron): This should be treated as the window closing.
+
+  // Because the process hosting this window has ended, close the window by
+  // sending the window close messages that the bridge would have sent.
+  OnWindowWillClose();
+  // Explicitly propagate this message to all children (they are also observers,
+  // but may not be destroyed before |this| is destroyed, which would violate
+  // tear-down assumptions). This would have been done by the bridge, had it
+  // shut down cleanly.
+  while (!children_.empty())
+    children_.front()->OnBridgeFactoryHostDestroying(host);
+  OnWindowHasClosed();
 }
 
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