Force slow objects for select objects during startup.

pkg/compiler/lib/src/js_emitter/old_emitter/emitter.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart2js.js_emitter;
 
 
 class OldEmitter implements Emitter {
   final Compiler compiler;
   final CodeEmitterTask task;
@@ skipping 313 matching lines @@
 
           var str = "function " + name + "(";
           var body = "";
           if (#hasIsolateSupport) { var fieldNames = ""; }
 
           for (var i = 0; i < fields.length; i++) {
             if(i != 0) str += ", ";
 
             var field = generateAccessor(fields[i], accessors, name);
             if (#hasIsolateSupport) { fieldNames += "'" + field + "',"; }
-            var parameter = "parameter_" + field;
+            var parameter = "p_" + field;
             str += parameter;
             body += ("this." + field + " = " + parameter + ";\n");
           }
           str += ") {\n" + body + "}\n";
           str += name + ".builtin$cls=\"" + name + "\";\n";
-          str += "$desc=$collectedClasses." + name + ";\n";
-          str += "if($desc instanceof Array) $desc = \$desc[1];\n";
+          str += "$desc=$collectedClasses." + name + "[1];\n";
           str += name + ".prototype = $desc;\n";
           if (typeof defineClass.name != "string") {
             str += name + ".name=\"" + name + "\";\n";
           }
           if (#hasIsolateSupport) {
             str += name + "." + #fieldNamesProperty + "=[" + fieldNames
                    + "];\n";
           }
           str += accessors.join("");
 
@@ skipping 67 matching lines @@
   }
 
   /** Needs defineClass to be defined. */
   jsAst.Expression buildInheritFrom() {
     jsAst.Expression result = js(r"""
         function() {
           function tmp() {}
           return function (constructor, superConstructor) {
             tmp.prototype = superConstructor.prototype;
             var object = new tmp();
+            object.x = 0; delete object.x; // Make object slow.

[floitsch, 2015/02/24 20:21:39]

I discussed and benchmarked this with Slava. It looks like setting the __proto__
is a good option.
Short term this is the easier fix, though.

[herhut, 2015/03/09 15:11:05]

Acknowledged.

             var properties = constructor.prototype;
             var members = Object.keys(properties);
             for (var i = 0; i < members.length; i++) {
               var member = members[i];
               object[member] = properties[member];
             }
             // Use a function for `true` here, as functions are stored in the
             // hidden class and not as properties in the object.
             object[#operatorIsPrefix + constructor.name] = constructor;
             object.constructor = constructor;
@@ skipping 1560 matching lines @@
     for (Element element in compiler.enqueuer.codegen.newlyEnqueuedElements) {
       if (element.isInstanceMember) {
         cachedClassBuilders.remove(element.enclosingClass);
 
         nativeEmitter.cachedBuilders.remove(element.enclosingClass);
 
       }
     }
   }
 }