Add ConstructorBodyEntity

pkg/compiler/lib/src/js_model/elements.dart

Index: pkg/compiler/lib/src/js_model/elements.dart
diff --git a/pkg/compiler/lib/src/js_model/elements.dart b/pkg/compiler/lib/src/js_model/elements.dart
index f156f056acb6eb3017e72f63100c48d33c2ce431..30244c06d019de9266f6598c5c4acf1970b08180 100644
--- a/pkg/compiler/lib/src/js_model/elements.dart
+++ b/pkg/compiler/lib/src/js_model/elements.dart
@@ -66,6 +66,7 @@ abstract class JsToFrontendMapBase implements JsToFrontendMap {
   TypeVariableEntity toFrontendTypeVariable(TypeVariableEntity typeVariable);
 }
 
+// TODO(johnniwinther): Merge this with [JsKernelToElementMap].
 class JsElementCreatorMixin {
   IndexedLibrary createLibrary(
       int libraryIndex, String name, Uri canonicalUri) {
@@ -109,6 +110,11 @@ class JsElementCreatorMixin {
         isFromEnvironmentConstructor: isFromEnvironmentConstructor);
   }
 
+  ConstructorBodyEntity createConstructorBody(
+      int memberIndex, ConstructorEntity constructor) {
+    return new JConstructorBody(memberIndex, constructor);
+  }
+
   IndexedFunction createGetter(int memberIndex, LibraryEntity library,
       ClassEntity enclosingClass, Name name, AsyncMarker asyncMarker,
       {bool isStatic, bool isExternal, bool isAbstract}) {
@@ -419,6 +425,26 @@ class JFactoryConstructor extends JConstructor {
   bool get isGenerativeConstructor => false;
 }
 
+class JConstructorBody extends JFunction implements ConstructorBodyEntity {
+  final ConstructorEntity constructor;
+
+  JConstructorBody(int memberIndex, this.constructor)
+      : super(
+            memberIndex,
+            constructor.library,
+            constructor.enclosingClass,
+            constructor.memberName,
+            constructor.parameterStructure,
+            AsyncMarker.SYNC,
+            isStatic: false,
+            isExternal: false);
+
+  @override
+  bool get isFunction => true;
+
+  String get _kind => 'constructor_body';
+}
+
 class JMethod extends JFunction {
   final bool isAbstract;