If textLength="" appears on a text content element whose children form multiple
chunks, the spacing or glyph adjustment is made only to the first chunk and not
spread across all chunks.

Example:

  <svg xmlns='http://www.w3.org/2000/svg' width='400' height='300'
       font-size='14'>
    <line x1='10' y1='130' x2='210' y2='130' stroke='blue'/>
    <line x1='10' y1='135' x2='76' y2='135' stroke='red'/>
    <text x='10' y='150' textLength='200'>
      abc<tspan x='10' y='170'>def</tspan><tspan x='10' y='190'>ghi</tspan>
    </text>
  </svg>

The three lines of text should be stretch approximately along the red line, but
the current behaviour stretches the first line of text along the blue line and
does not stretch the remaining two lines.