MathJax removes any aria-label put on input mathml

Created by: jcayzac

I've noticed that MathJax 2.2 doesn't copy aria-label attributes from the input MathML to the span element it creates:

<math aria-label="3 times the identity matrix">
    <apply>
        <times/>
        <cn> 0 </cn>
        <matrix>
            <matrixrow>
                <cn> 1 </cn> <cn> 0 </cn> <cn> 0 </cn>
            </matrixrow>
            <matrixrow>
                <cn> 0 </cn> <cn> 1 </cn> <cn> 0 </cn>
            </matrixrow>
            <matrixrow>
                <cn> 0 </cn> <cn> 0 </cn> <cn> 1 </cn>
            </matrixrow>
        </matrix>
    </apply>
</math>

…becomes:

<span class="MathJax_SVG" id="MathJax-Element-2-Frame" role="textbox" aria-readonly="true" style="font-size: 100%; display: inline-block;">
    <svg xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 -1968.8903908297991 6927.276651322095 3437.7807816595982" style="width: 16.107ex; height: 7.992ex; vertical-align: -3.443ex; margin: 1px 0px;">
        <g stroke="black" fill="black" stroke-width="0" transform="matrix(1 0 0 -1 0 0)">
            <use xlink:href="#MJMAIN-30">
            </use>
            <use xlink:href="#MJMAIN-2B" x="727" y="0">
            </use>
            <g transform="translate(1732,0)">
                <g transform="translate(0,1950)">
                    <use xlink:href="#MJSZ4-239B" x="0" y="-1165">
                    </use>
                    <use xlink:href="#MJSZ4-239D" x="0" y="-2746">
                    </use>
                </g>
                <g transform="translate(1047,0)">
                    <g transform="translate(-15,0)">
                        <use xlink:href="#MJMAIN-30" x="0" y="1150">
                        </use>
                        <use xlink:href="#MJMAIN-30" x="0" y="-50">
                        </use>
                        <use xlink:href="#MJMAIN-31" x="0" y="-1250">
                        </use>
                    </g>
                    <g transform="translate(1290,0)">
                        <use xlink:href="#MJMAIN-31" x="0" y="1150">
                        </use>
                        <use xlink:href="#MJMAIN-30" x="0" y="-50">
                        </use>
                        <use xlink:href="#MJMAIN-30" x="0" y="-1250">
                        </use>
                    </g>
                    <g transform="translate(2595,0)">
                        <use xlink:href="#MJMAIN-30" x="0" y="1150">
                        </use>
                        <use xlink:href="#MJMAIN-31" x="0" y="-50">
                        </use>
                        <use xlink:href="#MJMAIN-30" x="0" y="-1250">
                        </use>
                    </g>
                </g>
                <g transform="translate(4314,1950)">
                    <use xlink:href="#MJSZ4-239E" x="0" y="-1164">
                    </use>
                    <use xlink:href="#MJSZ4-23A0" x="0" y="-2746">
                    </use>
                </g>
            </g>
        </g>
    </svg>
</span>