Well spotted. `grep` tells me that it isn't used:
```
$ grep -r handleTileChange_ src
src/ol/map.js:      goog.bind(this.handleTileChange_, this));
src/ol/map.js:ol.Map.prototype.handleTileChange_ = function() {
src/ol/renderer/layerrenderer.js:ol.renderer.Layer.prototype.handleTileChange_ = function(event) {
```