tree of InlineStyle and InlineText elements.
StyledText builds an Inline that renders the tree.

For example this StyledText object:

  new StyledText(["FOO", [boldLargerStyle, [greenStyle "BAR"], "BAZ"] BORF]);

Renders the same way the following HTML would,
assuming that TextStyles boldLargerStyle and
greenStyle were defined.

<style>
div {
  display: inline;
}
</style>
<p>
  <div>
    FOO
    <div style="font-weight:bold; font-size:larger">
      <div style="color:green">
        BAR
      </div>
      BAZ
    </div>
    BORF
  </div>
</p>

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1194693002.