Introduce ConstructorEntity

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

Index: pkg/compiler/lib/src/elements/entities.dart
diff --git a/pkg/compiler/lib/src/elements/entities.dart b/pkg/compiler/lib/src/elements/entities.dart
index 6fd1f50d543fdc1536a855a9c13e99f0dc90f79f..b326f3537e4483940468d5729248f110d6a418c1 100644
--- a/pkg/compiler/lib/src/elements/entities.dart
+++ b/pkg/compiler/lib/src/elements/entities.dart
@@ -53,6 +53,17 @@ abstract class FieldEntity extends MemberEntity {}
 
 /// Stripped down super interface for function like entities.
 ///
-/// Currently only [FieldElement] but later also kernel based Dart constructors
+/// Currently only [MethodElement] but later also kernel based Dart constructors
 /// and methods and/or Dart-in-JS function-like properties.
 abstract class FunctionEntity extends MemberEntity {}
+
+/// Stripped down super interface for constructor like entities.
+///
+/// Currently only [ConstructorElement] but later also kernel based Dart
+/// constructors and/or Dart-in-JS constructor-like properties.
+// TODO(johnniwinther): Remove factory constructors from the set of
+// constructors.
+abstract class ConstructorEntity extends FunctionEntity {
+  bool get isGenerativeConstructor;
+  bool get isFactoryConstructor;
+}