Extract out a source_span package from source_maps.

pkg/source_span/lib/src/utils.dart

Index: pkg/source_span/lib/src/utils.dart
diff --git a/pkg/source_maps/lib/src/utils.dart b/pkg/source_span/lib/src/utils.dart
similarity index 64%
copy from pkg/source_maps/lib/src/utils.dart
copy to pkg/source_span/lib/src/utils.dart
index 78f098e70b194e6ad8211d8d1c8cb94b5f88a463..4a8eb551e5ca09a67c078a4e34a44719eb27bc64 100644
--- a/pkg/source_maps/lib/src/utils.dart
+++ b/pkg/source_span/lib/src/utils.dart
@@ -1,15 +1,24 @@
-// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// 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.
 
-/// Utilities that shouldn't be in this package.
-library source_maps.utils;
+library source_span.utils;
+
+/// Returns the minimum of [obj1] and [obj2] according to
+/// [Comparable.compareTo].
+Comparable min(Comparable obj1, Comparable obj2) =>
+    obj1.compareTo(obj2) > 0 ? obj2 : obj1;
+
+/// Returns the maximum of [obj1] and [obj2] according to
+/// [Comparable.compareTo].
+Comparable max(Comparable obj1, Comparable obj2) =>
+    obj1.compareTo(obj2) > 0 ? obj1 : obj2;
 
 /// Find the first entry in a sorted [list] that matches a monotonic predicate.
+///
 /// Given a result `n`, that all items before `n` will not match, `n` matches,
 /// and all items after `n` match too. The result is -1 when there are no
 /// items, 0 when all items match, and list.length when none does.
-// TODO(sigmund): remove this function after dartbug.com/5624 is fixed.
 int binarySearch(List list, bool matches(item)) {
   if (list.length == 0) return -1;
   if (matches(list.first)) return 0;
@@ -27,3 +36,4 @@ int binarySearch(List list, bool matches(item)) {
   }
   return max;
 }
+