Add file identifiers to summaries.

pkg/analyzer/tool/summary/idl_model.dart

Index: pkg/analyzer/tool/summary/idl_model.dart
diff --git a/pkg/analyzer/tool/summary/idl_model.dart b/pkg/analyzer/tool/summary/idl_model.dart
index fca10548665833e658191f242a4e36b96aa60bef..a583d647a26fcdb0372c92cfcbba9152a60b2d6d 100644
--- a/pkg/analyzer/tool/summary/idl_model.dart
+++ b/pkg/analyzer/tool/summary/idl_model.dart
@@ -23,7 +23,14 @@ class ClassDeclaration extends Declaration {
    */
   final bool isTopLevel;
 
-  ClassDeclaration(String documentation, String name, this.isTopLevel)
+  /**
+   * If [isTopLevel] is `true` and a file identifier was specified for this
+   * class, the file identifier string.  Otheswise `null`.
+   */
+  final String fileIdentifier;
+
+  ClassDeclaration(
+      String documentation, String name, this.isTopLevel, this.fileIdentifier)
       : super(documentation, name);
 }