-tr-property-ref replacement needs to work with gradient settings

We need to be able to use -tr-property-ref to do color replacements for color gradient assignments, like the following (showing examples for all browsers):

background: linear-gradient(top, #cce2f6 0%, #b1d2f2 100%);
background: -moz-linear-gradient(top, #cce2f6 0%, #b1d2f2 100%);
background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#cce2f6), color-stop(100%,#b1d2f2));
background: -webkit-linear-gradient(top, #cce2f6 0%, #b1d2f2 100%);
filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#cce2f6', endColorstr='#b1d2f2',GradientType=0 );
background: -ms-linear-gradient(top, #cce2f6 0%, #b1d2f2 100%);