Viewer tag not optional and horizontal scrolling only works with native

I like the option to have different viewers in the new version of embed pdf, but it doesn't work unless the viewer is specified, so it is not backwards compatible with v2.0 - it just displays the pdf statement without interpreting it. I have attached a pic. I've tested on Chrome, Firefox and IE.
Also, the native viewer option is the only one that will put on a horizontal scroll bar if the window shrinks smaller than the width of the pdf. Anyone know how to set that for google or pdfjs?