Placing a scrollable div below a fixed div of variable height

Question

This is with respect to a mobile page in jquery mobile

I have 2 divs as follows within a parent div(data-role=header)

Answer 1

CSS:

.inner-topHeader-panel {
  width: 100%;
  height: auto;
  margin: 20;
  background: white;
  border-bottom: none;
  float: left;
  clear: both;
  top: 0;
  z-index: 1000;
}
.inner-centercontent {
  width: 100%;
  float: left;
  height: 600px;
  overflow: scroll;
  padding-bottom: 50px;
}

Plunker

Will only scroll when height is smaller than inner content.