Making save a little faster:

compiler/java/com/google/dart/compiler/ast/DartNode.java

Index: compiler/java/com/google/dart/compiler/ast/DartNode.java
===================================================================
--- compiler/java/com/google/dart/compiler/ast/DartNode.java	(revision 14360)
+++ compiler/java/com/google/dart/compiler/ast/DartNode.java	(working copy)
@@ -41,7 +41,7 @@
   }
 
   @Override
-  public final String toString() {
+  public String toString() {
     return this.toSource();
   }
 
@@ -117,7 +117,10 @@
    * @param visitor the visitor that will be used to visit the child
    */
   protected void safelyVisitChild(DartNode child, ASTVisitor<?> visitor) {
-    if (child != null) {
+    // Inline the DartIdentifier path - it's by far the most common.
+    if (child instanceof DartIdentifier) {
+      visitor.visitIdentifier((DartIdentifier)child);
+    } else if (child != null) {
       child.accept(visitor);
     }
   }