Indeterminate progress

Consider having a common function e.g. transformProgress
```
transformProgress: function(progress, ratio) {
  var transform = 'scaleX(' + (ratio / 100) + ')';
  progress.style.transform = progress.style.webkitTransform = transform;
},

ratioChanged: function() {
  this.transformProgress(this.$.activeProgress, this.ratio);
},

secondaryRatioChanged: function() {
  this.transformProgress(this.$.secondaryProgress, this.secondaryRatio);
}
```