Copy files I'll use in a git-based CL.

dart/utils/compiler/source_file.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) 2012, 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.
 
 // TODO(jimhug): This should be an interface to work better with tools.
 /**
  * Represents a file of source code.
  */
 class SourceFile implements Comparable {
   // TODO(terry): This filename for in memory buffer.  May need to rework if
   //              filename is used for more than informational.
@@ skipping 165 matching lines @@
 
   /** Compares two source spans by file and position. Handles nulls. */
   int compareTo(SourceSpan other) {
     if (file == other.file) {
       int d = start - other.start;
       return d == 0 ? (end - other.end) : d;
     }
     return file.compareTo(other.file);
   }
 }