Handle synthetic nodes use to throw exceptions

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

Index: pkg/compiler/lib/src/js_backend/backend_helpers.dart
diff --git a/pkg/compiler/lib/src/js_backend/backend_helpers.dart b/pkg/compiler/lib/src/js_backend/backend_helpers.dart
index e50c7448bf6bf985fa7274d165c8aedfebe6644f..ee8d6965d18ab9940b249be191f01de567e8a5ea 100644
--- a/pkg/compiler/lib/src/js_backend/backend_helpers.dart
+++ b/pkg/compiler/lib/src/js_backend/backend_helpers.dart
@@ -215,6 +215,9 @@ class BackendHelpers {
     return element;
   }
 
+  Element findCoreHelper(String name) =>
+      compiler.commonElements.coreLibrary.implementation.localLookup(name);
+
   ConstructorElement _findConstructor(ClassElement cls, String name) {
     cls.ensureResolved(resolution);
     ConstructorElement constructor = cls.lookupConstructor(name);
@@ -633,6 +636,18 @@ class BackendHelpers {
     return findHelper('throwNoSuchMethod');
   }
 
+  Element get genericNoSuchMethod =>
+      _genericNoSuchMethod ??= findCoreHelper('_genericNoSuchMethod');
+  MethodElement _genericNoSuchMethod;
+
+  Element get unresolvedConstructorError => _unresolvedConstructorError ??=
+      findCoreHelper('_unresolvedConstructorError');
+  MethodElement _unresolvedConstructorError;
+
+  Element get malformedTypeError =>
+      _malformedTypeError ??= findCoreHelper('_malformedTypeError');
+  MethodElement _malformedTypeError;
+
   Element get createRuntimeType {
     return findHelper('createRuntimeType');
   }