Use entities in interceptor_stub_generator.

pkg/compiler/lib/src/js_backend/custom_elements_analysis.dart

Index: pkg/compiler/lib/src/js_backend/custom_elements_analysis.dart
diff --git a/pkg/compiler/lib/src/js_backend/custom_elements_analysis.dart b/pkg/compiler/lib/src/js_backend/custom_elements_analysis.dart
index a89b86d24b591a1f34254283fb11395e05ef446b..3a5534537fa5d5a322c9e948092af9378c7839c5 100644
--- a/pkg/compiler/lib/src/js_backend/custom_elements_analysis.dart
+++ b/pkg/compiler/lib/src/js_backend/custom_elements_analysis.dart
@@ -126,7 +126,7 @@ class CustomElementsAnalysis {
   bool needsClass(ClassElement classElement) =>
       codegenJoin.activeClasses.contains(classElement);
 
-  List<Element> constructors(ClassElement classElement) =>
+  List<ConstructorElement> constructors(ClassElement classElement) =>
       codegenJoin.computeEscapingConstructors(classElement);
 }