dart2js: add constructor for directly instatiated mixin classes in the new emitter.

pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart

Index: pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart b/pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart
index 6e37f27edaf5e9bce1be9c4199c4851c21c1f9f6..9d09af4829c5215e57b5db0278b8f15fe09076b2 100644
--- a/pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/new_emitter/model_emitter.dart
@@ -33,7 +33,6 @@ import '../js_emitter.dart' show NativeGenerator, buildTearOffCode;
 import '../model.dart';
 
 
-
 class ModelEmitter {
   final Compiler compiler;
   final Namer namer;
@@ -466,7 +465,8 @@ class ModelEmitter {
   // This string should be referenced wherever JavaScript code makes assumptions
   // on the mixin format.
   static final String mixinFormatDescription =
-      "Mixins have no constructor, but a reference to their mixin class.";
+      "Mixins have a reference to their mixin class followed by a constructor" +

[floitsch, 2015/02/06 12:41:19]

"Mixins have a reference to their mixin class at the place of the usual
constructor. If they are instantiated the constructor follows the reference."

[floitsch, 2015/02/06 12:41:20]

You don't need the "+" if two string literals are next to each other.

[zarah, 2015/02/06 14:27:09]

Done.

[zarah, 2015/02/06 14:27:09]

Done.

+      "function in the case they have been directly instatiated";

[floitsch, 2015/02/06 12:41:19]

"instantiated.";

[zarah, 2015/02/06 14:27:09]

Acknowledged.

 
   js.Expression emitClass(Class cls) {
     List elements = [js.string(cls.superclassName),
@@ -476,6 +476,9 @@ class ModelEmitter {
       MixinApplication mixin = cls;
       elements.add(js.string(mixin.mixinClass.name));
       elements.add(js.number(mixin.mixinClass.holder.index));
+      if (cls.isDirectlyInstantiated) {
+        elements.add(_generateConstructor(cls));
+      }
     } else {
       elements.add(_generateConstructor(cls));
     }
@@ -800,18 +803,28 @@ function parseFunctionDescriptor(proto, name, descriptor) {
     descriptor = compile(name, descriptor);
     var prototype = determinePrototype(descriptor);
     var constructor;
+    var functionsIndex;
     // $mixinFormatDescription.
     if (typeof descriptor[2] !== 'function') {
-      constructor = compileMixinConstructor(name, prototype, descriptor);
-      for (var i = 4; i < descriptor.length; i += 2) {
-        parseFunctionDescriptor(prototype, descriptor[i], descriptor[i + 1]);
+      compileMixinConstructor(name, prototype, descriptor);
+      // The mixin application has been directly instatiated and hence it has a

[floitsch, 2015/02/06 12:41:20]

// Descriptor[4] contains the constructor if the mixin application is directly
instantiated.

[zarah, 2015/02/06 14:27:09]

Done.

+      // construtor function.

[floitsch, 2015/02/06 12:41:19]

constructor

[zarah, 2015/02/06 14:27:09]

Acknowledged.

+      if (typeof descriptor[4] === 'function') {
+        constructor = descriptor[4];
+        functionsIndex = 5;
+      } else {
+        constructor = function() {};
+        functionsIndex = 4;
       }
     } else {
       constructor = descriptor[2];
-      for (var i = 3; i < descriptor.length; i += 2) {
-        parseFunctionDescriptor(prototype, descriptor[i], descriptor[i + 1]);
-      }
+      functionsIndex = 3;
     }
+
+    for (var i = functionsIndex; i < descriptor.length; i += 2) {
+      parseFunctionDescriptor(prototype, descriptor[i], descriptor[i + 1]);
+    }
+
     constructor.builtin\$cls = name;  // Needed for RTI.
     constructor.prototype = prototype;
     prototype[#operatorIsPrefix + name] = constructor;
@@ -832,10 +845,6 @@ function parseFunctionDescriptor(proto, name, descriptor) {
       var p = mixinProperties[i];
       prototype[p] = mixinPrototype[p];
     }
-    // Since this is a mixin application the constructor will actually never
-    // be invoked. We only use its prototype for the application's subclasses. 
-    var constructor = function() {};
-    return constructor;
   }
 
   function determinePrototype(descriptor) {