Optimize dartium dart:html bindings so real world application performance is acceptable. Improves d…

sdk/lib/js/dartium/js_dartium.dart

Index: sdk/lib/js/dartium/js_dartium.dart
diff --git a/sdk/lib/js/dartium/js_dartium.dart b/sdk/lib/js/dartium/js_dartium.dart
index 2c4ccd30880727f13dad0bb36f048efcf980c0ee..610ec2242e04977813e966f1a47a3ab9c7e686fe 100644
--- a/sdk/lib/js/dartium/js_dartium.dart
+++ b/sdk/lib/js/dartium/js_dartium.dart
@@ -92,6 +92,7 @@ import 'dart:nativewrappers';
 import 'dart:math' as math;
 import 'dart:mirrors' as mirrors;
 import 'dart:html' as html;
+import 'dart:_blink' as _blink;
 import 'dart:html_common' as html_common;
 import 'dart:indexed_db' as indexed_db;
 import 'dart:typed_data';
@@ -120,7 +121,7 @@ _buildArgs(Invocation invocation) {
       varArgs[mirrors.MirrorSystem.getName(symbol)] = val;
     });
     return invocation.positionalArguments.toList()
-      ..add(maybeWrapTypedInterop(new JsObject.jsify(varArgs)));
+      ..add(JsNative.jsify(varArgs));
   }
 }
 
@@ -401,12 +402,21 @@ String _accessJsPathHelper(Iterable<String> parts) {
   return sb.toString();
 }
 
+// TODO(jacobr): remove these helpers and add JsNative.setPropertyDotted,
+// getPropertyDotted, and callMethodDotted helpers that would be simpler
+// and more efficient.
 String _accessJsPathSetter(String path) {
   var parts = path.split(".");
   return "${_JS_LIBRARY_PREFIX}.JsNative.setProperty(${_accessJsPathHelper(parts.getRange(0, parts.length - 1))
       }, '${parts.last}', v)";
 }
 
+String _accessJsPathCallMethodHelper(String path) {
+  var parts = path.split(".");
+  return "${_JS_LIBRARY_PREFIX}.JsNative.callMethod(${_accessJsPathHelper(parts.getRange(0, parts.length - 1))
+      }, '${parts.last}',";
+}
+
 @Deprecated("Internal Use Only")
 void addMemberHelper(
     mirrors.MethodMirror declaration, String path, StringBuffer sb,
@@ -426,11 +436,11 @@ void addMemberHelper(
   sb.write(" ");
   if (declaration.isGetter) {
     sb.write(
-        "get $name => ${_JS_LIBRARY_PREFIX}.maybeWrapTypedInterop(${_accessJsPath(path)});");
+        "get $name => ${_accessJsPath(path)};");
   } else if (declaration.isSetter) {
     sb.write("set $name(v) {\n"
         "  ${_JS_LIBRARY_PREFIX}.safeForTypedInterop(v);\n"
-        "  return ${_JS_LIBRARY_PREFIX}.maybeWrapTypedInterop(${_accessJsPathSetter(path)});\n"
+        "  return ${_accessJsPathSetter(path)};\n"
         "}\n");
   } else {
     sb.write("$name(");
@@ -463,19 +473,19 @@ void addMemberHelper(
     for (var arg in args) {
       sb.write("  ${_JS_LIBRARY_PREFIX}.safeForTypedInterop($arg);\n");
     }
-    sb.write("  return ${_JS_LIBRARY_PREFIX}.maybeWrapTypedInterop(");
+    sb.write("  return ");
     if (declaration.isConstructor) {
-      sb.write("new ${_JS_LIBRARY_PREFIX}.JsObject(");
+      sb.write("${_JS_LIBRARY_PREFIX}.JsNative.callConstructor(");
+      sb..write(_accessJsPath(path))..write(",");
+    } else {
+      sb.write(_accessJsPathCallMethodHelper(path));
     }
-    sb
-      ..write(_accessJsPath(path))
-      ..write(declaration.isConstructor ? "," : ".apply(")
-      ..write("[${args.join(",")}]");
+    sb.write("[${args.join(",")}]");
 
     if (hasOptional) {
       sb.write(".takeWhile((i) => i != ${_UNDEFINED_VAR}).toList()");
     }
-    sb.write("));");
+    sb.write(");");
     sb.write("}\n");
   }
   sb.write("\n");
@@ -562,7 +572,7 @@ _generateLibraryCodegen(uri, library, staticCodegen) {
                     ..write('}');
                 }
                 sbPatch.write(") {\n"
-                    "    var ret = new ${_JS_LIBRARY_PREFIX}.JsObject.jsify({});\n");
+                    "    var ret = ${_JS_LIBRARY_PREFIX}.JsNative.newObject();\n");
                 i = 0;
                 for (var p in declaration.parameters) {
                   assert(p.isNamed); // TODO(jacobr): throw.
@@ -571,14 +581,14 @@ _generateLibraryCodegen(uri, library, staticCodegen) {
                       mirrors.MirrorSystem.getName(p.simpleName));
                   sbPatch.write("    if($name != ${_UNDEFINED_VAR}) {\n"
                       "      ${_JS_LIBRARY_PREFIX}.safeForTypedInterop($name);\n"
-                      "      ret['$jsName'] = $name;\n"
+                      "      ${_JS_LIBRARY_PREFIX}.JsNative.setProperty(ret, '$jsName', $name);\n"
                       "    }\n");
                   i++;
                 }
 
                 sbPatch.write(
-                    "    return new ${_JS_LIBRARY_PREFIX}.JSObject.create(ret);\n"
-                    "  }\n");
+                  "  return ret;"
+                  "}\n");
               } else if (declaration.isConstructor ||
                   declaration.isFactoryConstructor) {
                 sbPatch.write("  ");
@@ -607,8 +617,7 @@ _generateLibraryCodegen(uri, library, staticCodegen) {
             });
           }
           if (isDom) {
-            sbPatch.write("  factory ${className}._internalWrap() => "
-                "new ${classNameImpl}.internal_();\n");
+            sbPatch.write("  static Type get instanceRuntimeType => ${classNameImpl};\n");
           }
           if (sbPatch.isNotEmpty) {
             var typeVariablesClause = '';
@@ -757,27 +766,15 @@ abstract class JSObjectInterfacesDom $implementsClauseDom {
 }
 
 patch class JSObject {
-  factory JSObject.create(JsObject jsObject) {
-    var ret = new JSObjectImpl.internal()..blink_jsObject = jsObject;
-    jsObject._dartHtmlWrapper = ret;
-    return ret;
-  }
+  static Type get instanceRuntimeType => JSObjectImpl;
 }
 
 patch class JSFunction {
-  factory JSFunction.create(JsObject jsObject) {
-    var ret = new JSFunctionImpl.internal()..blink_jsObject = jsObject;
-    jsObject._dartHtmlWrapper = ret;
-    return ret;
-  }
+  static Type get instanceRuntimeType => JSFunctionImpl;
 }
 
 patch class JSArray {
-  factory JSArray.create(JsObject jsObject) {
-    var ret = new JSArrayImpl.internal()..blink_jsObject = jsObject;
-    jsObject._dartHtmlWrapper = ret;
-    return ret;
-  }
+  static Type get instanceRuntimeType => JSArrayImpl;
 }
 
 _registerAllJsInterfaces() {
@@ -959,49 +956,44 @@ JsObject get context {
   return _cachedContext;
 }
 
-@Deprecated("Internal Use Only")
-maybeWrapTypedInterop(o) => html_common.wrap_jso_no_SerializedScriptvalue(o);
-
-_maybeWrap(o) {
-  var wrapped = html_common.wrap_jso_no_SerializedScriptvalue(o);
-  if (identical(wrapped, o)) return o;
-  return (wrapped is html.Blob ||
-      wrapped is html.Event ||
-      wrapped is indexed_db.KeyRange ||
-      wrapped is html.ImageData ||
-      wrapped is html.Node ||
-      wrapped is TypedData ||
-      wrapped is html.Window) ? wrapped : o;
-}
-
-/**
- * Get the dart wrapper object for object. Top-level so we
- * we can access it from other libraries without it being
- * a public instance field on JsObject.
- */
-@Deprecated("Internal Use Only")
-getDartHtmlWrapperFor(JsObject object) => object._dartHtmlWrapper;
-
-/**
- * Set the dart wrapper object for object. Top-level so we
- * we can access it from other libraries without it being
- * a public instance field on JsObject.
- */
-@Deprecated("Internal Use Only")
-void setDartHtmlWrapperFor(JsObject object, wrapper) {
-  object._dartHtmlWrapper = wrapper;
+_lookupType(o, bool isCrossFrame, bool isElement) {
+  try {
+   var type = html_common.lookupType(o, isElement);
+   var typeMirror = mirrors.reflectType(type);
+   var legacyInteropConvertToNative = typeMirror.isSubtypeOf(mirrors.reflectType(html.Blob)) ||
+        typeMirror.isSubtypeOf(mirrors.reflectType(html.Event)) ||
+        typeMirror.isSubtypeOf(mirrors.reflectType(indexed_db.KeyRange)) ||
+        typeMirror.isSubtypeOf(mirrors.reflectType(html.ImageData)) ||
+        typeMirror.isSubtypeOf(mirrors.reflectType(html.Node)) ||
+//        TypedData is removed from this list as it is converted directly
+//        rather than flowing through the interceptor code path.
+//        typeMirror.isSubtypeOf(mirrors.reflectType(typed_data.TypedData)) ||
+        typeMirror.isSubtypeOf(mirrors.reflectType(html.Window));
+    if (isCrossFrame && !typeMirror.isSubtypeOf(mirrors.reflectType(html.Window))) {
+      // TODO(jacobr): evaluate using the true cross frame Window class, etc.
+      // as well as triggering that legacy JS Interop returns raw JsObject
+      // instances.
+      legacyInteropConvertToNative = false;
+    }
+    return [type, legacyInteropConvertToNative];
+  } catch (e) { }
+  return [JSObject.instanceRuntimeType, false];
 }
 
 /**
- * Used by callMethod to get the JS object for each argument passed if the
- * argument is a Dart class instance that delegates to a DOM object.  See
- * wrap_jso defined in dart:html.
+ * Base class for both the legacy JsObject class and the modern JSObject class.
+ * This allows the JsNative utility class tobehave identically whether it is
+ * called on a JsObject or a JSObject.
  */
-@Deprecated("Internal Use Only")
-unwrap_jso(dartClass_instance) {
-  if (dartClass_instance is JSObject &&
-      dartClass_instance is! JsObject) return dartClass_instance.blink_jsObject;
-  else return dartClass_instance;
+class _JSObjectBase extends NativeFieldWrapperClass2 {
+  String _toString() native "JSObject_toString";
+  _callMethod(String name, List args) native "JSObject_callMethod";
+  _operator_getter(String property) native "JSObject_[]";
+  _operator_setter(String property, value) native "JSObject_[]=";
+  bool _hasProperty(String property) native "JsObject_hasProperty";
+  bool _instanceof(/*JsFunction|JSFunction*/ type) native "JsObject_instanceof";
+
+  int get hashCode native "JSObject_hashCode";
 }
 
 /**
@@ -1010,22 +1002,16 @@ unwrap_jso(dartClass_instance) {
  * The properties of the JavaScript object are accessible via the `[]` and
  * `[]=` operators. Methods are callable via [callMethod].
  */
-class JsObject extends NativeFieldWrapperClass2 {
+class JsObject extends _JSObjectBase {
   JsObject.internal();
 
   /**
-   * If this JsObject is wrapped, e.g. DOM objects, then we can save the
-   * wrapper here and preserve its identity.
-   */
-  var _dartHtmlWrapper;
-
-  /**
    * Constructs a new JavaScript object from [constructor] and returns a proxy
    * to it.
    */
   factory JsObject(JsFunction constructor, [List arguments]) {
     try {
-      return html_common.unwrap_jso(_create(constructor, arguments));
+      return _create(constructor, arguments);
     } catch (e) {
       // Re-throw any errors (returned as a string) as a DomException.
       throw new html.DomException.jsInterop(e);
@@ -1050,6 +1036,7 @@ class JsObject extends NativeFieldWrapperClass2 {
     if (object is num || object is String || object is bool || object == null) {
       throw new ArgumentError("object cannot be a num, string, bool, or null");
     }
+    if (object is JsObject) return object;
     return _fromBrowserObject(object);
   }
 
@@ -1071,7 +1058,7 @@ class JsObject extends NativeFieldWrapperClass2 {
 
   static JsObject _jsify(object) native "JsObject_jsify";
 
-  static JsObject _fromBrowserObject(object) => html_common.unwrap_jso(object);
+  static JsObject _fromBrowserObject(object) native "JsObject_fromBrowserObject";
 
   /**
    * Returns the value associated with [property] from the proxied JavaScript
@@ -1081,14 +1068,14 @@ class JsObject extends NativeFieldWrapperClass2 {
    */
   operator [](property) {
     try {
-      return _maybeWrap(_operator_getter(property));
+      return _operator_getterLegacy(property);
     } catch (e) {
       // Re-throw any errors (returned as a string) as a DomException.
       throw new html.DomException.jsInterop(e);
     }
   }
 
-  _operator_getter(property) native "JsObject_[]";
+  _operator_getterLegacy(property) native "JsObject_[]Legacy";
 
   /**
    * Sets the value associated with [property] on the proxied JavaScript
@@ -1098,27 +1085,23 @@ class JsObject extends NativeFieldWrapperClass2 {
    */
   operator []=(property, value) {
     try {
-      _operator_setter(property, value);
+      _operator_setterLegacy(property, value);
     } catch (e) {
       // Re-throw any errors (returned as a string) as a DomException.
       throw new html.DomException.jsInterop(e);
     }
   }
 
-  _operator_setter(property, value) native "JsObject_[]=";
+  _operator_setterLegacy(property, value) native "JsObject_[]=Legacy";
 
   int get hashCode native "JsObject_hashCode";
 
   operator ==(other) {
-    var is_JsObject = other is JsObject;
-    if (!is_JsObject) {
-      other = html_common.unwrap_jso(other);
-      is_JsObject = other is JsObject;
-    }
-    return is_JsObject && _identityEquality(this, other);
+    if (other is! JsObject && other is! JSObject) return false;
+    return _identityEquality(this, other);
   }
 
-  static bool _identityEquality(JsObject a, JsObject b)
+  static bool _identityEquality(a, b)
       native "JsObject_identityEquality";
 
   /**
@@ -1127,7 +1110,7 @@ class JsObject extends NativeFieldWrapperClass2 {
    *
    * This is the equivalent of the `in` operator in JavaScript.
    */
-  bool hasProperty(String property) native "JsObject_hasProperty";
+  bool hasProperty(String property) => _hasProperty(property);
 
   /**
    * Removes [property] from the JavaScript object.
@@ -1141,7 +1124,7 @@ class JsObject extends NativeFieldWrapperClass2 {
    *
    * This is the equivalent of the `instanceof` operator in JavaScript.
    */
-  bool instanceof(JsFunction type) native "JsObject_instanceof";
+  bool instanceof(JsFunction type) => _instanceof(type);
 
   /**
    * Returns the result of the JavaScript objects `toString` method.
@@ -1164,7 +1147,7 @@ class JsObject extends NativeFieldWrapperClass2 {
    */
   callMethod(String method, [List args]) {
     try {
-      return _maybeWrap(_callMethod(method, args));
+      return _callMethodLegacy(method, args);
     } catch (e) {
       if (hasProperty(method)) {
         // Return a DomException if DOM call returned an error.
@@ -1175,19 +1158,26 @@ class JsObject extends NativeFieldWrapperClass2 {
     }
   }
 
-  _callMethod(String name, List args) native "JsObject_callMethod";
+  _callMethodLegacy(String name, List args) native "JsObject_callMethodLegacy";
 }
 
+
 /// Base class for all JS objects used through dart:html and typed JS interop.
 @Deprecated("Internal Use Only")
-class JSObject {
+class JSObject extends _JSObjectBase {
   JSObject.internal() {}
-  external factory JSObject.create(JsObject jsObject);
-
-  @Deprecated("Internal Use Only")
-  JsObject blink_jsObject;
+  external static Type get instanceRuntimeType;
 
-  String toString() => blink_jsObject.toString();
+  /**
+   * Returns the result of the JavaScript objects `toString` method.
+   */
+  String toString() {
+    try {
+      return _toString();
+    } catch (e) {
+      return super.toString();
+    }
+  }
 
   noSuchMethod(Invocation invocation) {
     throwError() {
@@ -1204,7 +1194,7 @@ class JSObject {
             !_allowedMethods.containsKey(invocation.memberName)) {
           throwError();
         }
-        var ret = maybeWrapTypedInterop(blink_jsObject._operator_getter(name));
+        var ret = _operator_getter(name);
         if (matches != null) return ret;
         if (ret is Function ||
             (ret is JsFunction /* shouldn't be needed in the future*/) &&
@@ -1213,7 +1203,7 @@ class JSObject {
         throwError();
       } else {
         // TODO(jacobr): should we throw if the JavaScript object doesn't have the property?
-        return maybeWrapTypedInterop(blink_jsObject._operator_getter(name));
+        return _operator_getter(name);
       }
     } else if (invocation.isSetter) {
       if (CHECK_JS_INVOCATIONS) {
@@ -1223,8 +1213,7 @@ class JSObject {
       }
       assert(name.endsWith("="));
       name = name.substring(0, name.length - 1);
-      return maybeWrapTypedInterop(blink_jsObject._operator_setter(
-          name, invocation.positionalArguments.first));
+      return _operator_setter(name, invocation.positionalArguments.first);
     } else {
       // TODO(jacobr): also allow calling getters that look like functions.
       var matches;
@@ -1233,8 +1222,7 @@ class JSObject {
         if (matches == null ||
             !matches.checkInvocation(invocation)) throwError();
       }
-      var ret = maybeWrapTypedInterop(
-          blink_jsObject._callMethod(name, _buildArgs(invocation)));
+      var ret = _callMethod(name, _buildArgs(invocation));
       if (CHECK_JS_INVOCATIONS) {
         if (!matches._checkReturnType(ret)) {
           html.window.console.error("Return value for method: ${name} is "
@@ -1250,21 +1238,56 @@ class JSObject {
 @Deprecated("Internal Use Only")
 class JSArray extends JSObject with ListMixin {
   JSArray.internal() : super.internal();
-  external factory JSArray.create(JsObject jsObject);
-  operator [](int index) =>
-      maybeWrapTypedInterop(JsNative.getArrayIndex(blink_jsObject, index));
+  external static Type get instanceRuntimeType;
+
+  // Reuse JsArray_length as length behavior is unchanged.
+  int get length native "JsArray_length";
+
+  set length(int length) {
+    _operator_setter('length', length);
+  }
+
+  _checkIndex(int index, {bool insert: false}) {
+    int length = insert ? this.length + 1 : this.length;
+    if (index is int && (index < 0 || index >= length)) {
+      throw new RangeError.range(index, 0, length);
+    }
+  }
+
+  _checkRange(int start, int end) {
+    int cachedLength = this.length;
+    if (start < 0 || start > cachedLength) {
+      throw new RangeError.range(start, 0, cachedLength);
+    }
+    if (end < start || end > cachedLength) {
+      throw new RangeError.range(end, start, cachedLength);
+    }
+  }
 
-  operator []=(int index, value) => blink_jsObject[index] = value;
+  _indexed_getter(int index) native "JSArray_indexed_getter";
+  _indexed_setter(int index, o) native "JSArray_indexed_setter";
+
+  // Methods required by ListMixin
+
+  operator [](index) {
+    if (index is int) {
+      _checkIndex(index);
+    }
+
+    return _indexed_getter(index);
+  }
 
-  int get length => blink_jsObject.length;
-  set length(int newLength) => blink_jsObject.length = newLength;
+  void operator []=(int index, value) {
+    _checkIndex(index);
+    _indexed_setter(index, value);
+  }
 }
 
 @Deprecated("Internal Use Only")
 class JSFunction extends JSObject implements Function {
   JSFunction.internal() : super.internal();
 
-  external factory JSFunction.create(JsObject jsObject);
+  external static Type get instanceRuntimeType;
 
   call(
       [a1 = _UNDEFINED,
@@ -1277,48 +1300,49 @@ class JSFunction extends JSObject implements Function {
       a8 = _UNDEFINED,
       a9 = _UNDEFINED,
       a10 = _UNDEFINED]) {
-    return maybeWrapTypedInterop(blink_jsObject
-        .apply(_stripUndefinedArgs([a1, a2, a3, a4, a5, a6, a7, a8, a9, a10])));
+    return _apply(_stripUndefinedArgs([a1, a2, a3, a4, a5, a6, a7, a8, a9, a10]));
   }
 
   noSuchMethod(Invocation invocation) {
     if (invocation.isMethod && invocation.memberName == #call) {
-      return maybeWrapTypedInterop(
-          blink_jsObject.apply(_buildArgs(invocation)));
+      return _apply(_buildArgs(invocation));
     }
     return super.noSuchMethod(invocation);
   }
+
+  dynamic _apply(List args, {thisArg}) native "JSFunction_apply";
+
+  static JSFunction _createWithThis(Function f) native "JSFunction_createWithThis";
+  static JSFunction _create(Function f) native "JSFunction_create";
 }
 
 // JavaScript interop methods that do not automatically wrap to dart:html types.
 // Warning: this API is not exposed to dart:js.
+// TODO(jacobr): rename to JSNative and make at least part of this API public.
 @Deprecated("Internal Use Only")
 class JsNative {
-  static getProperty(o, name) {
-    o = unwrap_jso(o);
-    return o != null ? o._operator_getter(name) : null;
-  }
+  static JSObject jsify(object) native "JSObject_jsify";
+  static JSObject newObject() native "JSObject_newObject";
+  static JSArray newArray() native "JSObject_newArray";
 
-  static setProperty(o, name, value) {
-    return unwrap_jso(o)._operator_setter(name, value);
-  }
-
-  static callMethod(o, String method, List args) {
-    return unwrap_jso(o)._callMethod(method, args);
-  }
+  static hasProperty(_JSObjectBase o, name) => o._hasProperty(name);
+  static getProperty(_JSObjectBase o, name) => o._operator_getter(name);
+  static setProperty(_JSObjectBase o, name, value) => o._operator_setter(name, value);
+  static callMethod(_JSObjectBase o, String method, List args) => o._callMethod(method, args);
+  static instanceof(_JSObjectBase o, /*JsFunction|JSFunction*/ type) => o._instanceof(type);
+  static callConstructor0(_JSObjectBase constructor) native "JSNative_callConstructor0";
+  static callConstructor(_JSObjectBase constructor, List args) native "JSNative_callConstructor";
 
-  static getArrayIndex(JsArray array, int index) {
-    array._checkIndex(index);
-    return getProperty(array, index);
-  }
+  static toTypedObject(JsObject o) native "JSNative_toTypedObject";
 
   /**
    * Same behavior as new JsFunction.withThis except that JavaScript "this" is not
    * wrapped.
    */
-  static JsFunction withThis(Function f) native "JsFunction_withThisNoWrap";
+  static JSFunction withThis(Function f) native "JsFunction_withThisNoWrap";
 }
 
+
 /**
  * Proxies a JavaScript Function object.
  */
@@ -1336,7 +1360,7 @@ class JsFunction extends JsObject {
    * supplied it is the value of `this` for the invocation.
    */
   dynamic apply(List args, {thisArg}) =>
-      _maybeWrap(_apply(args, thisArg: thisArg));
+      _apply(args, thisArg: thisArg);
 
   dynamic _apply(List args, {thisArg}) native "JsFunction_apply";
 
@@ -1488,15 +1512,6 @@ void argsSafeForTypedInterop(Iterable args) {
   }
 }
 
-List _stripAndWrapArgs(Iterable args) {
-  var ret = [];
-  for (var arg in args) {
-    if (arg == _UNDEFINED) break;
-    ret.add(maybeWrapTypedInterop(arg));
-  }
-  return ret;
-}
-
 /**
  * Returns a method that can be called with an arbitrary number (for n less
  * than 11) of arguments without violating Dart type checks.
@@ -1515,90 +1530,6 @@ Function _wrapAsDebuggerVarArgsFunction(JsFunction jsFunction) => (
     jsFunction._applyDebuggerOnly(
         _stripUndefinedArgs([a1, a2, a3, a4, a5, a6, a7, a8, a9, a10]));
 
-/// This helper is purely a hack so we can reuse JsFunction.withThis even when
-/// we don't care about passing JS "this". In an ideal world we would implement
-/// helpers in C++ that directly implement allowInterop and
-/// allowInteropCaptureThis.
-class _CreateDartFunctionForInteropIgnoreThis implements Function {
-  Function _fn;
-
-  _CreateDartFunctionForInteropIgnoreThis(this._fn);
-
-  call(
-      [ignoredThis = _UNDEFINED,
-      a1 = _UNDEFINED,
-      a2 = _UNDEFINED,
-      a3 = _UNDEFINED,
-      a4 = _UNDEFINED,
-      a5 = _UNDEFINED,
-      a6 = _UNDEFINED,
-      a7 = _UNDEFINED,
-      a8 = _UNDEFINED,
-      a9 = _UNDEFINED,
-      a10 = _UNDEFINED]) {
-    var ret = Function.apply(
-        _fn, _stripAndWrapArgs([a1, a2, a3, a4, a5, a6, a7, a8, a9, a10]));
-    safeForTypedInterop(ret);
-    return ret;
-  }
-
-  noSuchMethod(Invocation invocation) {
-    if (invocation.isMethod && invocation.memberName == #call) {
-      // Named arguments not yet supported.
-      if (invocation.namedArguments.isNotEmpty) return;
-      var ret = Function.apply(
-          _fn, _stripAndWrapArgs(invocation.positionalArguments.skip(1)));
-      // TODO(jacobr): it would be nice to check that the return value is safe
-      // for interop but we don't want to break existing addEventListener users.
-      // safeForTypedInterop(ret);
-      safeForTypedInterop(ret);
-      return ret;
-    }
-    return super.noSuchMethod(invocation);
-  }
-}
-
-/// See comment for [_CreateDartFunctionForInteropIgnoreThis].
-/// This Function exists purely because JsObject doesn't have the DOM type
-/// conversion semantics we want for JS typed interop.
-class _CreateDartFunctionForInterop implements Function {
-  Function _fn;
-
-  _CreateDartFunctionForInterop(this._fn);
-
-  call(
-      [a1 = _UNDEFINED,
-      a2 = _UNDEFINED,
-      a3 = _UNDEFINED,
-      a4 = _UNDEFINED,
-      a5 = _UNDEFINED,
-      a6 = _UNDEFINED,
-      a7 = _UNDEFINED,
-      a8 = _UNDEFINED,
-      a9 = _UNDEFINED,
-      a10 = _UNDEFINED]) {
-    var ret = Function.apply(
-        _fn, _stripAndWrapArgs([a1, a2, a3, a4, a5, a6, a7, a8, a9, a10]));
-    safeForTypedInterop(ret);
-    return ret;
-  }
-
-  noSuchMethod(Invocation invocation) {
-    if (invocation.isMethod && invocation.memberName == #call) {
-      // Named arguments not yet supported.
-      if (invocation.namedArguments.isNotEmpty) return;
-      var ret = Function.apply(
-          _fn, _stripAndWrapArgs(invocation.positionalArguments));
-      safeForTypedInterop(ret);
-      return ret;
-    }
-    return super.noSuchMethod(invocation);
-  }
-}
-
-/// Cached JSFunction associated with the Dart Function.
-Expando<JSFunction> _interopExpando = new Expando<JSFunction>();
-
 /// Returns a wrapper around function [f] that can be called from JavaScript
 /// using the package:js Dart-JavaScript interop.
 ///
@@ -1615,14 +1546,7 @@ JSFunction allowInterop(Function f) {
     // The function is already a JSFunction... no need to do anything.
     return f;
   } else {
-    var ret = _interopExpando[f];
-    if (ret == null) {
-      // TODO(jacobr): we could optimize this.
-      ret = new JSFunction.create(new JsFunction.withThis(
-          new _CreateDartFunctionForInteropIgnoreThis(f)));
-      _interopExpando[f] = ret;
-    }
-    return ret;
+    return JSFunction._create(f);
   }
 }
 
@@ -1646,10 +1570,11 @@ JSFunction allowInteropCaptureThis(Function f) {
     var ret = _interopCaptureThisExpando[f];
     if (ret == null) {
       // TODO(jacobr): we could optimize this.
-      ret = new JSFunction.create(
-          new JsFunction.withThis(new _CreateDartFunctionForInterop(f)));
+      ret = JSFunction._createWithThis(f);
       _interopCaptureThisExpando[f] = ret;
     }
     return ret;
   }
 }
+
+debugPrint(_) {}