Roll Observatory packages and add a roll script

charted/lib/charts/chart_legend.dart

-//
-// Copyright 2014 Google Inc. All rights reserved.
-//
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file or at
-// https://developers.google.com/open-source/licenses/bsd
-//
-
-part of charted.charts;
-
-///
-/// Interface that is implemented by classes that support
-/// displaying legend.
-///
-abstract class ChartLegend {
-  /// Title of the legend, dynamically updates the legend title when set.
-  String title;
-
-  /// Called by [ChartArea] to notify changes to legend.
-  update(Iterable<ChartLegendItem> legend, ChartArea chart);
-
-  /// Called by [ChartArea] to dispose selection listeners.
-  dispose();
-
-  /// Factory to create an instance of the default implementation.
-  factory ChartLegend(Element host,
-      {maxItems: 0, title: '', showValues: false}) =>
-          new DefaultChartLegendImpl(host, maxItems, showValues, title);
-}
-
-///
-/// Class representing an item in the legend.
-///
-class ChartLegendItem {
-  /// Index of the row/column in [ChartData]. Legend uses column based coloring
-  /// in [CartesianArea] that has useRowColoring set to false and row based
-  /// coloring in all other cases.
-  int index;
-
-  /// HTML color used for the row/column in chart
-  String color;
-
-  /// The label of the item.
-  String label;
-
-  /// Description of the item.
-  String description;
-
-  /// Pre-formatted value to use as value.
-  String value;
-
-  /// List of series that this column is part of
-  Iterable<ChartSeries> series;
-
-  ChartLegendItem({this.index, this.color,
-      this.label, this.description, this.series, this.value});
-}