Revert "Add native_testing library to mock @Native classes"

sdk/lib/_internal/js_runtime/lib/native_helper.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of _js_helper;
 
 
 // TODO(ngeoffray): stop using this method once our optimizers can
 // change str1.contains(str2) into str1.indexOf(str2) != -1.
 bool contains(String userAgent, String name) {
@@ skipping 431 matching lines @@
 // JavaScript code fragments.
 //
 // This is a temporary place for the JavaScript code.
 //
 // TODO(sra): These code fragments are not minified.  They could be generated by
 // the code emitter, or JS_CONST could be improved to parse entire functions and
 // take care of the minification.
 
 const _baseHooks = const JS_CONST(r'''
 function() {
-  var toStringFunction = Object.prototype.toString;
-  function getTag(o) {
-    var s = toStringFunction.call(o);
+  function typeNameInChrome(o) {
+    var constructor = o.constructor;
+    if (constructor) {
+      var name = constructor.name;
+      if (name) return name;
+    }
+    var s = Object.prototype.toString.call(o);
     return s.substring(8, s.length - 1);
   }
   function getUnknownTag(object, tag) {
     // This code really belongs in [getUnknownTagGenericBrowser] but having it
     // here allows [getUnknownTag] to be tested on d8.
     if (/^HTML[A-Z].*Element$/.test(tag)) {
       // Check that it is not a simple JavaScript object.
-      var name = toStringFunction.call(object);
+      var name = Object.prototype.toString.call(object);
       if (name == "[object Object]") return null;
       return "HTMLElement";
     }
   }
   function getUnknownTagGenericBrowser(object, tag) {
     if (self.HTMLElement && object instanceof HTMLElement) return "HTMLElement";
     return getUnknownTag(object, tag);
   }
   function prototypeForTag(tag) {
     if (typeof window == "undefined") return null;
     if (typeof window[tag] == "undefined") return null;
     var constructor = window[tag];
     if (typeof constructor != "function") return null;
     return constructor.prototype;
   }
   function discriminator(tag) { return null; }
 
   var isBrowser = typeof navigator == "object";
 
   return {
-    getTag: getTag,
+    getTag: typeNameInChrome,
     getUnknownTag: isBrowser ? getUnknownTagGenericBrowser : getUnknownTag,
     prototypeForTag: prototypeForTag,
     discriminator: discriminator };
 }''');
 
 
 /**
  * Returns the name of the constructor function for browsers where
  * `object.constructor.name` is not reliable.
  *
@@ skipping 151 matching lines @@
 const _safariHooksTransformer = const JS_CONST(r'''
 function(hooks) { return hooks; }
 ''');
 
 
 const _dartExperimentalFixupGetTagHooksTransformer = const JS_CONST(r'''
 function(hooks) {
   if (typeof dartExperimentalFixupGetTag != "function") return hooks;
   hooks.getTag = dartExperimentalFixupGetTag(hooks.getTag);
 }''');