Dispatch a synthetic mouse exit to the widget handling mouse events when a widget grabs capture

ui/aura/window_tree_host.cc

Index: ui/aura/window_tree_host.cc
diff --git a/ui/aura/window_tree_host.cc b/ui/aura/window_tree_host.cc
index 9ac7cf7ab0182634013b2794ca9716ea9692330f..5565f1033f1668681eac8e90195b5c316dad71eb 100644
--- a/ui/aura/window_tree_host.cc
+++ b/ui/aura/window_tree_host.cc
@@ -150,8 +150,10 @@ void WindowTreeHost::OnCursorVisibilityChanged(bool show) {
   // visible because that can only happen in response to a mouse event, which
   // will trigger its own mouse enter.
   if (!show) {
-    dispatcher()->DispatchMouseExitAtPoint(
+    ui::EventDispatchDetails details = dispatcher()->DispatchMouseExitAtPoint(
         dispatcher()->GetLastMouseLocationInRoot());
+    if (details.dispatcher_destroyed)
+      return;
   }
 
   OnCursorVisibilityChangedNative(show);