Better feature-testing for Chrome browser

sdk/lib/_internal/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 466 matching lines @@
 /**
  * Returns the name of the constructor function for browsers where
  * `object.constructor.name` is not reliable.
  *
  * This function is split out of [_fallbackConstructorHooksTransformerGenerator]
  * as it is called from both the dispatch hooks and via
  * [constructorNameFallback] from objectToString.
  */
 const _constructorNameFallback = const JS_CONST(r'''
 function getTagFallback(o) {
-  if (o == null) return "Null";
   var constructor = o.constructor;
   if (typeof constructor == "function") {
-    var name = constructor.builtin$cls;
-    if (typeof name == "string") return name;
-    // The constructor is not null or undefined at this point. Try
-    // to grab hold of its name.
     name = constructor.name;
     // If the name is a non-empty string, we use that as the type name of this
     // object. On Firefox, we often get "Object" as the constructor name even
     // for more specialized objects so we have to fall through to the toString()
     // based implementation below in that case.
     if (typeof name == "string"
         && name !== ""
         && name !== "Object"
         && name !== "Function.prototype") {  // Can happen in Opera.
       return name;
     }
   }
   var s = Object.prototype.toString.call(o);
   return s.substring(8, s.length - 1);
 }''');
 
 
 const _fallbackConstructorHooksTransformerGenerator = const JS_CONST(r'''
 function(getTagFallback) {
   return function(hooks) {
     // If we are not in a browser, assume we are in d8.
     // TODO(sra): Recognize jsshell.
     if (typeof navigator != "object") return hooks;
 
-    var userAgent = navigator.userAgent;
+    var ua = navigator.userAgent;
     // TODO(antonm): remove a reference to DumpRenderTree.
-    if (userAgent.indexOf("Chrome") >= 0 ||
-        userAgent.indexOf("DumpRenderTree") >= 0) {
-      return hooks;
+    if (ua.indexOf("DumpRenderTree") >= 0) return hooks;
+    if (ua.indexOf("Chrome") >= 0) {
+      // Confirm constructor name is usable for dispatch.
+      function confirm(p) {
+        return typeof window == "object" && window[p] && window[p].name == p;
+      }
+      if (confirm("Window") && confirm("HTMLElement")) return hooks;
     }
 
     hooks.getTag = getTagFallback;
   };
 }''');
 
 
 const _ieHooksTransformer = const JS_CONST(r'''
 function(hooks) {
   var userAgent = typeof navigator == "object" ? navigator.userAgent : "";
@@ skipping 72 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);
 }''');