Add native_testing library to mock @Native classes

tests/html/html.status

Index: tests/html/html.status
diff --git a/tests/html/html.status b/tests/html/html.status
index 419e7bbcb19aa2de85d14cdf5597469362f0dcc4..b3aece5e5559be5299d801b1933a385309e1c422 100644
--- a/tests/html/html.status
+++ b/tests/html/html.status
@@ -14,6 +14,8 @@ js_typed_interop_type2_test: Fail, OK # tests dart2js-specific behavior.
 js_typed_interop_type3_test: Fail, OK # tests dart2js-specific behavior.
 
 native_gc_test: Skip # Dartium JSInterop failure
+js_interop_constructor_name_test/HTMLDivElement-methods: Fail # Investigate.
+js_interop_constructor_name_test/HTMLDivElement-types: Fail # ditto
 
 [ $compiler == none && ($runtime == drt || $runtime == dartium ) ]
 worker_api_test: Fail # Issue 10223
@@ -32,7 +34,8 @@ mirrors_js_typed_interop_test: Pass, Slow
 js_type_test/dynamic-null-not-Foo: Fail  # Issue 26838
 js_type_test/dynamic-String-not-Foo: Fail  # Issue 26838
 js_type_test/dynamic-String-not-dynamic-Foo: Fail  # Issue 26838
-
+js_interop_constructor_name_test/HTMLDivElement-types-erroneous1: Fail # Issue 26838
+js_interop_constructor_name_test/HTMLDivElement-types-erroneous2: Fail # Issue 26838
 
 [ $compiler == dart2js && $checked ]
 js_function_getter_trust_types_test: Skip # --trust-type-annotations incompatible with --checked