Backtracking regexes have pathological worst-case performance when
a long line contains a large amount of whitespace not followed by
a newline, since the regex engine will attempt to match the regex
at each whitespace character, read ahead to the non-whitespace non-
newline, declare no match, and try again at the next whitespace.
E.g. try running
util.removeTrailingSpaces(new Array(1e6).join(' ') + 'a').length
which would hang V8.
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