dynamic text field - turn on scrolling/scrollbars html

I have XML text data loading into a multiline dynamic text field. But I need the text field to have scrollbars as the text is bigger than the size of the canvas. I tried putting the code below in the style in the head of the html document. But it doesn't do anything to the text field (this code has worked in other html documents outside of animate). 

Thank you for any tips.

::-webkit-scrollbar {
width: 7px;
}

::-webkit-scrollbar-track {
-webkit-box-shadow: inset 0 0 6px rgba(0,0,0,1.00);

}

::-webkit-scrollbar-thumb {

-webkit-box-shadow: inset 0 0 6px rgba(0,0,0,1.00);
background-color: rgba(250,250,250,1.00);
}