Add support for Element.docRange to the summary.

pkg/analyzer/tool/summary/idl.dart

Index: pkg/analyzer/tool/summary/idl.dart
diff --git a/pkg/analyzer/tool/summary/idl.dart b/pkg/analyzer/tool/summary/idl.dart
index 0e2b84b76663c90dfaa582dd08bb586115ddf4b5..3d966604a50eb0da0f9148172b5c8cd8a85adbb7 100644
--- a/pkg/analyzer/tool/summary/idl.dart
+++ b/pkg/analyzer/tool/summary/idl.dart
@@ -304,6 +304,17 @@ class UnlinkedDocumentationComment {
    * specially encoded.
    */
   String text;
+
+  /**
+   * Offset of the beginning of the documentation comment relative to the
+   * beginning of the file.
+   */
+  int offset;
+
+  /**
+   * Length of the documentation comment (prior to replacing '\r\n' with '\n').
+   */
+  int length;
 }
 
 /**