Make patching of classes lazy.

lib/compiler/implementation/scanner/class_element_parser.dart

Index: lib/compiler/implementation/scanner/class_element_parser.dart
diff --git a/lib/compiler/implementation/scanner/class_element_parser.dart b/lib/compiler/implementation/scanner/class_element_parser.dart
index 02f6eaab530429b9ea26a40f8ea34c8083672ed1..4b9045c4b0b4632c73ade4086debb531ee423ac6 100644
--- a/lib/compiler/implementation/scanner/class_element_parser.dart
+++ b/lib/compiler/implementation/scanner/class_element_parser.dart
@@ -22,12 +22,20 @@ class PartialClassElement extends ClassElement {
 
   ClassNode parseNode(DiagnosticListener diagnosticListener) {
     if (cachedNode != null) return cachedNode;
+    // TODO(ahe): Measure these tasks.
     MemberListener listener = new MemberListener(diagnosticListener, this);
     Parser parser = new ClassElementParser(listener);
     Token token = parser.parseTopLevelDeclaration(beginToken);
     assert(token === endToken.next);
     cachedNode = listener.popNode();
     assert(listener.nodes.isEmpty());
+    if (isPatched) {
+      // TODO(lrn): Perhaps extract functionality so it doesn't need compiler.
+      Compiler compiler = diagnosticListener;
+      ClassNode patchNode = compiler.patchParser.parsePatchClassNode(patch);
+      Link<Element> patches = patch.localMembers;
+      compiler.applyContainerPatch(this, patches);
+    }
     return cachedNode;
   }