avoid page break inside row of table

You might try this with CSS:

<table class="print-friendly">
 <!-- The rest of your table here -->
</table>

<style>
    table.print-friendly tr td, table.print-friendly tr th {
        page-break-inside: avoid;
    }
</style>

Most CSS rules don't apply to <tr> tags directly, because of exactly what you pointed out above - they have a unique display style, which doesn't allow for these CSS rules. However, the <td> and <th> tags within them usually do allow this kind of specification - and you can easily apply such rules to ALL child-<tr>'s and <td>'s using CSS as shown above.

I used the 4px trick by @AaronHill above (link) and it worked really well! I used though a simpler css rule without needing to add a class to each <td> in the table.

@media print {
    table tbody tr td:before,
    table tbody tr td:after {
        content: "";
        height: 4px;
        display: block;
    }
}

The best way I have found to deal with this problem in webkit browsers is to put a div inside each td element and apply the page-break-inside: avoid style to the div, like this:

...
<td>
  <div class="avoid">
    Cell content.
  </div>
</td>
...
<style type="text/css">
  .avoid {
    page-break-inside: avoid !important;
    margin: 4px 0 4px 0;  /* to keep the page break from cutting too close to the text in the div */
  }
</style>

Even though Chrome supposedly does not recognize the 'page-break-inside: avoid;' property, this seems to keep the row content from being split in half by a page break when using wktohtml to generate PDFs. The tr element may hang over the page break a bit, but the div and anything inside it will not.