code: function( binding, rootUuid, trackName ) {
  
  		var bindingsByRoot = this._bindingsByRootAndName,
  			bindingByName = bindingsByRoot[ rootUuid ],
  
  			bindings = this._bindings;
  
  		if ( bindingByName === undefined ) {
  
  			bindingByName = {};
  			bindingsByRoot[ rootUuid ] = bindingByName;
  
  		}
  
  		bindingByName[ trackName ] = binding;
  
  		binding._cacheIndex = bindings.length;
  		bindings.push( binding );
  
  	}
docs: Memory management for PropertyMixer objects