Roll Observatory packages and add a roll script

source_span/lib/src/location_mixin.dart

-// Copyright (c) 2015, 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 source_span.location_mixin;
-
-import 'location.dart';
-import 'span.dart';
-
-// Note: this class duplicates a lot of functionality of [SourceLocation]. This
-// is because in order for SourceLocation to use SourceLocationMixin,
-// SourceLocationMixin couldn't implement SourceLocation. In SourceSpan we
-// handle this by making the class itself non-extensible, but that would be a
-// breaking change for SourceLocation. So until we want to endure the pain of
-// cutting a release with breaking changes, we duplicate the code here.
-
-/// A mixin for easily implementing [SourceLocation].
-abstract class SourceLocationMixin implements SourceLocation {
-  String get toolString {
-    var source = sourceUrl == null ? 'unknown source' : sourceUrl;
-    return '$source:${line + 1}:${column + 1}';
-  }
-
-  int distance(SourceLocation other) {
-    if (sourceUrl != other.sourceUrl) {
-      throw new ArgumentError("Source URLs \"${sourceUrl}\" and "
-          "\"${other.sourceUrl}\" don't match.");
-    }
-    return (offset - other.offset).abs();
-  }
-
-  SourceSpan pointSpan() => new SourceSpan(this, this, "");
-
-  int compareTo(SourceLocation other) {
-    if (sourceUrl != other.sourceUrl) {
-      throw new ArgumentError("Source URLs \"${sourceUrl}\" and "
-          "\"${other.sourceUrl}\" don't match.");
-    }
-    return offset - other.offset;
-  }
-
-  bool operator ==(other) =>
-      other is SourceLocation &&
-      sourceUrl == other.sourceUrl &&
-      offset == other.offset;
-
-  int get hashCode => sourceUrl.hashCode + offset;
-
-  String toString() => '<$runtimeType: $offset $toolString>';
-}
-