All strong mode cleaning of dart2js.

pkg/compiler/lib/src/universe/element_world_builder.dart

Index: pkg/compiler/lib/src/universe/element_world_builder.dart
diff --git a/pkg/compiler/lib/src/universe/element_world_builder.dart b/pkg/compiler/lib/src/universe/element_world_builder.dart
index 4b3ae199e8ab54f26b91d6d907206e51c84822fb..50beb8c671da5bc485dda6e3d8d6537097976a8e 100644
--- a/pkg/compiler/lib/src/universe/element_world_builder.dart
+++ b/pkg/compiler/lib/src/universe/element_world_builder.dart
@@ -74,7 +74,7 @@ class ElementResolutionWorldBuilder extends ResolutionWorldBuilderBase {
                   .addInstantiation(constructor, instance.type, instance.kind);
             } else {
               ConstructorElement target = constructor.effectiveTarget;
-              ResolutionInterfaceType targetType =
+              ResolutionDartType targetType =
                   constructor.computeEffectiveTargetType(instance.type);
               ClassElement cls = target.enclosingClass;
               bool isNative = _nativeBasicData.isNativeClass(cls);
@@ -86,8 +86,10 @@ class ElementResolutionWorldBuilder extends ResolutionWorldBuilderBase {
               } else {
                 kind = Instantiation.DIRECTLY_INSTANTIATED;
               }
-              infoFor(targetType.element)
-                  .addInstantiation(target, targetType, kind);
+              if (targetType is ResolutionInterfaceType) {
+                infoFor(targetType.element)
+                    .addInstantiation(target, targetType, kind);
+              }
             }
           }
         });