gistfile1.js

// What I did

$myField.resizable({
    handles: ['.ui-resizable-handle'],        // I already have this as a jQuery object, but passing it threw an error
    alsoResize: '#'+myFieldId+' .scrollPane', // No way to specify the containment, so I had to add prepend the field ID. (allowing a jQuery object would fix that as well)
    containment: 'parent',                    // This keeps the width from getting wider
    resize: function() {
        $(this).width('100%');                // This keeps the width from getting narrower
        $('.scrollPane', this).width('100%'); // This keeps the alsoResize elements from changing widths
    }
});


// What I should have been able to do

$myField.resizable({
    handles: $myResizeHandle,                 // since jQuery objects can contain multiple elements, no array should be needed if passing one
    alsoResize: $('.scrollPane', $myField),   // much cleaner and scablable
    axis: 'y'                                 // replaces my 'containment' option and 'resize' event
});