Fix some build breaks.

tools/dom/templates/html/dartium/html_dartium.darttemplate

 // 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.
 
 // DO NOT EDIT
 // Auto-generated dart:html library.
 
 /**
  * HTML elements and other resources for web-based applications that need to
  * interact with the browser and the DOM (Document Object Model).
@@ skipping 397 matching lines @@
     // Try the most general type conversions on it.
     // TODO(alanknight): We may be able to do better. This maintains identity,
     // which is useful, but expensive. And if we nest something that only
     // this conversion handles, how does that work? e.g. a list of maps of elements.
     var converted = convertNativeToDart_SerializedScriptValue(jsObject);
     if (!identical(converted, jsObject)) {
       return converted;
     }
 
     var constructor = js.JsNative.getProperty(jsObject, 'constructor');
-    if (__interop_checks) {
-      debug_or_assert("constructor != null", constructor != null);
+    if (constructor == null) {
+      // Perfectly valid case for JavaScript objects where __proto__ has
+      // intentionally been set to null.
+      js.setDartHtmlWrapperFor(jsObject, jsObject);
+      return jsObject;
     }
     var jsTypeName = js.JsNative.getProperty(constructor, 'name');
-    if (__interop_checks) {
-      debug_or_assert("constructor != null && jsTypeName.length > 0", constructor != null && jsTypeName.length > 0);
+    if (jsTypeName is! String || jsTypeName.length == 0) {
+      // Not an html type.
+      js.setDartHtmlWrapperFor(jsObject, jsObject);
+      return jsObject;
     }
 
     var dartClass_instance;
     if (jsObject.hasProperty('dart_class')) {
       // Got a dart_class (it's a custom element) use it it's already set up
       // make sure it's upgraded.
       dartClass_instance = _upgradeHtmlElement(jsObject['dart_class']);
     } else {
       var localName = jsObject['localName'];
       var customElementClass = _knownCustomeElements[localName];
@@ skipping 49 matching lines @@
       return wrapper;
     }
 
     if (jsObject is js.JsArray) {
       var wrappingList = new _DartHtmlWrappingList(jsObject);
       js.setDartHtmlWrapperFor(jsObject, wrappingList);
       return wrappingList;
     }
 
     var constructor = js.JsNative.getProperty(jsObject, 'constructor');
-    if (__interop_checks) {
-      debug_or_assert("constructor != null", constructor != null);
+    if (constructor == null) {
+      // Perfectly valid case for JavaScript objects where __proto__ has
+      // intentionally been set to null.
+      js.setDartHtmlWrapperFor(jsObject, jsObject);
+      return jsObject;
     }
     var jsTypeName = js.JsNative.getProperty(constructor, 'name');
-    if (__interop_checks) {
-      debug_or_assert("constructor != null && jsTypeName.length > 0", constructor != null && jsTypeName.length > 0);
+    if (jsTypeName is! String || jsTypeName.length == 0) {
+      // Not an html type.
+      js.setDartHtmlWrapperFor(jsObject, jsObject);
+      return jsObject;
     }
 
     var func = getHtmlCreateFunction(jsTypeName);
     if (func != null) {
       var dartClass_instance = func();
       dartClass_instance.blink_jsObject = jsObject;
       js.setDartHtmlWrapperFor(jsObject, dartClass_instance);
       return dartClass_instance;
     }
     return jsObject;
@@ skipping 175 matching lines @@
 
 unwrap_jso(dartClass_instance) => dartClass_instance;
 wrap_jso(jsObject) => jsObject;
 make_dart_rectangle(r) => r;
 convertDartToNative_Dictionary(Map dict) => dict;
 List convertDartToNative_StringArray(List<String> input) => input;
 convertDartToNative_List(List input) => input;
 createCustomUpgrader(Type customElementClass, $this) => $this;
 
 $endif