makeSymbol = function(value, style, mode, color, classes) {
                    // Replace the value with its replaced value from symbol.js
                    if (symbols[mode][value] && symbols[mode][value].replace) {
                        value = symbols[mode][value].replace;
                    }

                    var metrics = fontMetrics.getCharacterMetrics(value, style);

                    var symbolNode;
                    if (metrics) {
                        symbolNode = new domTree.symbolNode(
                            value, metrics.height, metrics.depth, metrics.italic, metrics.skew,
                            classes);
                    } else {
                        // TODO(emily): Figure out a good way to only print this in development
                        typeof console !== "undefined" && console.warn(
                            "No character metrics for '" + value + "' in style '" +
                            style + "'");
                        symbolNode = new domTree.symbolNode(value, 0, 0, 0, 0, classes);
                    }

                    if (color) {
                        symbolNode.style.color = color;
                    }

                    return symbolNode;
                }
Makes an element placed in each of the vlist elements to ensure that each
element has the same max font size. To do this, we create a zero-width space
with the correct font size.