Recognize "patch" identifier in .dartp files.

lib/compiler/implementation/elements/elements.dart

Index: lib/compiler/implementation/elements/elements.dart
diff --git a/lib/compiler/implementation/elements/elements.dart b/lib/compiler/implementation/elements/elements.dart
index ad690789f5fbb8c414a1ab6995d0c5cfe0b77fdc..d754f838d80723628769cccf6b7c726eca0a08c0 100644
--- a/lib/compiler/implementation/elements/elements.dart
+++ b/lib/compiler/implementation/elements/elements.dart
@@ -102,6 +102,7 @@ class Element implements Hashable {
   final SourceString name;
   final ElementKind kind;
   final Element enclosingElement;
+  Link<Node> metadata = const EmptyLink<Node>();
   Modifiers get modifiers() => null;
 
   Node parseNode(DiagnosticListener listener) {
@@ -112,6 +113,10 @@ class Element implements Hashable {
     compiler.internalError("$this.computeType.", token: position());
   }
 
+  void addMetadata(Node node) {
+    metadata = metadata.prepend(node);
+  }
+
   bool isFunction() => kind === ElementKind.FUNCTION;
   bool isMember() =>
       enclosingElement !== null && enclosingElement.kind === ElementKind.CLASS;