code: function() {
          if (this.grid) {
              for(var iRow=0, len=this.grid.length; iRow<len; iRow++) {
                  var row = this.grid[iRow];
                  for(var iCol=0, clen=row.length; iCol<clen; iCol++) {
                      var tile = row[iCol];
                      this.destroyTile(tile);
                  }
              }
              this.grid = [];
              this.gridResolution = null;
              this.gridLayout = null;
          }
      }
docs: APIMethod: mergeNewParams
  Refetches tiles with new params merged, keeping a backbuffer. Each
  loading new tile will have a css class of '.olTileReplacing'. If a
  stylesheet applies a 'display: none' style to that class, any fade-in
  transition will not apply, and backbuffers for each tile will be removed
  as soon as the tile is loaded.
  
  Parameters:
  newParams - {Object}
  
  Returns:
  redrawn: {Boolean} whether the layer was actually redrawn.
   
  Method: clearGrid
  Go through and remove all tiles from the grid, calling
  destroy() on each of them to kill circular references