Inline special case of inheritFrom to call site.

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

Index: pkg/compiler/lib/src/js_emitter/old_emitter/emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/old_emitter/emitter.dart b/pkg/compiler/lib/src/js_emitter/old_emitter/emitter.dart
index bbce58a28536a7dc6a33645df781061ec2993511..9d5be9da87f9d2fcd7221bb7c1c31535c25d9b32 100644
--- a/pkg/compiler/lib/src/js_emitter/old_emitter/emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/old_emitter/emitter.dart
@@ -424,13 +424,6 @@ class OldEmitter implements Emitter {
         function() {
           function tmp() {}
           return function (constructor, superConstructor) {
-            if (superConstructor == null) {
-              // Fix up the the Dart Object class' prototype.
-              var prototype = constructor.prototype;
-              prototype.constructor = constructor;
-              prototype.#isObject = constructor;
-              return prototype;
-            }
             tmp.prototype = superConstructor.prototype;
             var object = new tmp();
             var properties = constructor.prototype;
@@ -447,8 +440,7 @@ class OldEmitter implements Emitter {
             return object;
           };
         }()
-      """, { 'operatorIsPrefix' : js.string(namer.operatorIsPrefix),
-             'isObject' : namer.operatorIs(compiler.objectClass) });
+      """, { 'operatorIsPrefix' : js.string(namer.operatorIsPrefix)});
     if (compiler.hasIncrementalSupport) {
       result = js(
           r'#.inheritFrom = #', [namer.accessIncrementalHelper, result]);
@@ -512,7 +504,12 @@ class OldEmitter implements Emitter {
         // the Object.prototype object, and they show through here, so we check
         // that we have a string.
         if (!superclass || typeof superclass != "string") {
-          inheritFrom(allClasses[cls], null);
+          // Inlined special case of InheritFrom here for performance reasons.
+          // Fix up the the Dart Object class' prototype.
+          var constructor = allClasses[cls];
+          var prototype = constructor.prototype;
+          prototype.constructor = constructor;
+          prototype.#isObject = constructor;
           return;
         }
         finishClass(superclass);
@@ -531,7 +528,8 @@ class OldEmitter implements Emitter {
     }''', {'finishedClassesAccess': finishedClassesAccess,
            'needsMixinSupport': needsMixinSupport,
            'hasNativeClasses': hasNativeClasses,
-           'nativeInfoHandler': nativeInfoHandler});
+           'nativeInfoHandler': nativeInfoHandler,
+           'isObject' : namer.operatorIs(compiler.objectClass) });
   }
 
   void emitFinishIsolateConstructorInvocation(CodeOutput output) {