Roll Observatory packages and add a roll script

dart_style/lib/src/source_code.dart

-// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-library dart_style.src.source_code;
-
-/// Describes a chunk of source code that is to be formatted or has been
-/// formatted.
-class SourceCode {
-  /// The [uri] where the source code is from.
-  ///
-  /// Used in error messages if the code cannot be parsed.
-  final String uri;
-
-  /// The Dart source code text.
-  final String text;
-
-  /// Whether the source is a compilation unit or a bare statement.
-  final bool isCompilationUnit;
-
-  /// The offset in [text] where the selection begins, or `null` if there is
-  /// no selection.
-  final int selectionStart;
-
-  /// The number of selected characters or `null` if there is no selection.
-  final int selectionLength;
-
-  /// Gets the source code before the beginning of the selection.
-  ///
-  /// If there is no selection, returns [text].
-  String get textBeforeSelection {
-    if (selectionStart == null) return text;
-    return text.substring(0, selectionStart);
-  }
-
-  /// Gets the selected source code, if any.
-  ///
-  /// If there is no selection, returns an empty string.
-  String get selectedText {
-    if (selectionStart == null) return "";
-    return text.substring(selectionStart, selectionStart + selectionLength);
-  }
-
-  /// Gets the source code following the selection.
-  ///
-  /// If there is no selection, returns an empty string.
-  String get textAfterSelection {
-    if (selectionStart == null) return "";
-    return text.substring(selectionStart + selectionLength);
-  }
-
-  SourceCode(this.text,
-      {this.uri,
-      this.isCompilationUnit: true,
-      this.selectionStart,
-      this.selectionLength}) {
-    // Must either provide both selection bounds or neither.
-    if ((selectionStart == null) != (selectionLength == null)) {
-      throw new ArgumentError(
-          "Is selectionStart is provided, selectionLength must be too.");
-    }
-
-    if (selectionStart != null) {
-      if (selectionStart < 0) {
-        throw new ArgumentError("selectionStart must be non-negative.");
-      }
-
-      if (selectionStart > text.length) {
-        throw new ArgumentError("selectionStart must be within text.");
-      }
-    }
-
-    if (selectionLength != null) {
-      if (selectionLength < 0) {
-        throw new ArgumentError("selectionLength must be non-negative.");
-      }
-
-      if (selectionStart + selectionLength > text.length) {
-        throw new ArgumentError("selectionLength must end within text.");
-      }
-    }
-  }
-}