Use originalGetTag on wrapped object

pkg/web_components/lib/dart_support.js

 // Copyright (c) 2014, 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.
 
 (function() {
   var ShadowDOMPolyfill = window.ShadowDOMPolyfill;
   if (!ShadowDOMPolyfill) return;
 
   if (navigator.userAgent.indexOf('(Dart)') !== -1) {
     console.error("ShadowDOMPolyfill polyfill was loaded in Dartium. This " +
         "will not work. This indicates that Dartium's Chrome version is " +
         "not compatible with this version of web_components.");
   }
 
   var needsConstructorFix = window.constructor === window.Window;
 
   // TODO(jmesserly): we need to wrap document somehow (a dart:html hook?)
-  window.dartExperimentalFixupGetTag = function(originalGetTag) {
+
+  // dartNativeDispatchHooksTransformer is described on initHooks() in
+  // sdk/lib/_internal/lib/native_helper.dart.
+  if (typeof window.dartNativeDispatchHooksTransformer == 'undefined')
+    window.dartNativeDispatchHooksTransformer = [];
+
+  window.dartNativeDispatchHooksTransformer.push(function(hooks) {
     var NodeList = ShadowDOMPolyfill.wrappers.NodeList;
     var ShadowRoot = ShadowDOMPolyfill.wrappers.ShadowRoot;
     var unwrapIfNeeded = ShadowDOMPolyfill.unwrapIfNeeded;
-    function getTag(obj) {
+    var originalGetTag = hooks.getTag;
+    hooks.getTag = function getTag(obj) {
       // TODO(jmesserly): do we still need these?
       if (obj instanceof NodeList) return 'NodeList';
       if (obj instanceof ShadowRoot) return 'ShadowRoot';
       if (MutationRecord && (obj instanceof MutationRecord))
           return 'MutationRecord';
       if (MutationObserver && (obj instanceof MutationObserver))
           return 'MutationObserver';
 
       // TODO(jmesserly): this prevents incorrect interaction between ShadowDOM
       // and dart:html's <template> polyfill. Essentially, ShadowDOM is
       // polyfilling native template, but our Dart polyfill fails to detect this
       // because the unwrapped node is an HTMLUnknownElement, leading it to
       // think the node has no content.
       if (obj instanceof HTMLTemplateElement) return 'HTMLTemplateElement';
 
       var unwrapped = unwrapIfNeeded(obj);
       if (unwrapped && (needsConstructorFix || obj !== unwrapped)) {
         // Fix up class names for Firefox, or if using the minified polyfill.
         // dart2js prefers .constructor.name, but there are all kinds of cases
         // where this will give the wrong answer.
         var ctor = obj.constructor
         if (ctor === unwrapped.constructor) {
           var name = ctor._ShadowDOMPolyfill$cacheTag_;
           if (!name) {
-            name = Object.prototype.toString.call(unwrapped);
-            name = name.substring(8, name.length - 1);
+            name = originalGetTag(unwrapped);

[Jennifer Messerly, 2014/05/13 21:01:31]

Interesting! Do we still need ctor._ShadowDOMPolyfill$cacheTag_ ? It seems like
we're willing to `return originalGetTag(obj);` below so I'm guessing it's not
needed. We could replace everything starting from line 52 to 57 (in the new
code) with just `return originalGetTag(unwrapped);`

I'm not sure if that then allows even more code folding with line 62 or not...

anyway, cool to see the Firefox code needs less workarounds now!

[Siggi Cherem (dart-lang), 2014/05/13 21:06:58]

+1, lgtm, if we don't need the caching, I'm happy to get rid of it too :)

[Siggi Cherem (dart-lang), 2014/05/13 21:55:21]

FYI - we chatted more about it offline and decided to keep the cashing for now
(even though we removed the toString here, it is still used underneath, so
caching it might not be a bad idea, we can measure and revisit if we want
later).

[Jennifer Messerly, 2014/05/13 22:12:36]

interesting. yeah, seems okay, but makes me wonder why we don't cache for
everything then?

FWIW -- I thought in the old dart2js code, "originalGetTag" did cache. At least,
that was my understanding when I reviewed the dart2js code at the time, and
reason it does not attempt caching below.

             ctor._ShadowDOMPolyfill$cacheTag_ = name;
           }
           return name;
         }
 
         obj = unwrapped;
       }
       return originalGetTag(obj);
     }
-
-    return getTag;
-  };
+  });
 })();