The browser reads document.title back with its whitespace stripped and
collapsed, so a title with two spaces in a row, a tab or a space at the
edge never reads back as written. useDocumentTitle put its title back on
every <head> mutation whenever the two differed, and its own write was
such a mutation: an endless loop that froze the tab at full CPU, for
example on opening a message whose subject has two spaces in a row. It
now also accepts what the browser read back after its own write.
dealerweb
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