Add error condition INVALID_OVERLAY_CHANGE to analysis server.

pkg/analysis_server/lib/src/protocol.dart

Index: pkg/analysis_server/lib/src/protocol.dart
diff --git a/pkg/analysis_server/lib/src/protocol.dart b/pkg/analysis_server/lib/src/protocol.dart
index 1f139e06b781b40d5d29e1eb0a0ac2cf2b3b7f05..e0b19b61d50f758cad1cefb72091c418ff72e444 100644
--- a/pkg/analysis_server/lib/src/protocol.dart
+++ b/pkg/analysis_server/lib/src/protocol.dart
@@ -130,6 +130,9 @@ List<AnalysisError> _analysisErrorListFromEngine(engine.LineInfo lineInfo,
  * SourceEdit.apply().
  */
 String _applyEdit(String code, SourceEdit edit) {
+  if (edit.length < 0) {
+    throw new RangeError('length is negative');
+  }
   return code.substring(0, edit.offset) +
       edit.replacement +
       code.substring(edit.end);