VM: [Kernel] Make NativeFieldWrapperClass[1-4] constructible when running from Kernel.

sdk/lib/html/dartium/nativewrappers.dart

Index: sdk/lib/html/dartium/nativewrappers.dart
diff --git a/sdk/lib/html/dartium/nativewrappers.dart b/sdk/lib/html/dartium/nativewrappers.dart
index 441749c6b66ebc76d5ac7de7a4650d0a653c4e1d..0d4e1119048cebdd516b9136d2a6485d8f98f0b5 100644
--- a/sdk/lib/html/dartium/nativewrappers.dart
+++ b/sdk/lib/html/dartium/nativewrappers.dart
@@ -4,31 +4,10 @@
 
 library nativewrappers;
 
-class NativeFieldWrapperClass1 {
-  NativeFieldWrapperClass1() {
-    throw new UnsupportedError(
-        "Generative constructors not supported on native types.");
-  }
-}
+class NativeFieldWrapperClass1 { }
 
-class NativeFieldWrapperClass2 {
-  NativeFieldWrapperClass2() {
-    throw new UnsupportedError(
-        "Generative constructors not supported on native types.");
-  }
-}
+class NativeFieldWrapperClass2 { }
 
-class NativeFieldWrapperClass3 {
-  NativeFieldWrapperClass3() {
-    throw new UnsupportedError(
-        "Generative constructors not supported on native types.");
-  }
-}
-
-class NativeFieldWrapperClass4 {
-  NativeFieldWrapperClass4() {
-    throw new UnsupportedError(
-        "Generative constructors not supported on native types.");
-  }
-}
+class NativeFieldWrapperClass3 { }
 
+class NativeFieldWrapperClass4 { }