Morph the APIs for Node, ParentNode, and Element closer to the specs

sky/engine/tonic/dart_converter.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SKY_ENGINE_TONIC_DART_CONVERTER_H_
 #define SKY_ENGINE_TONIC_DART_CONVERTER_H_
 
 #include <string>
 #include "sky/engine/tonic/dart_state.h"
 #include "sky/engine/tonic/dart_string.h"
@@ skipping 230 matching lines @@
   }
 
   static Vector<T> FromDart(Dart_Handle handle) {
     Vector<T> result;
     if (!Dart_IsList(handle))
       return result;
     intptr_t length = 0;
     Dart_ListLength(handle, &length);
     result.reserveCapacity(length);
     for (intptr_t i = 0; i < length; ++i) {
-      Dart_Handle element = Dart_ListGetAt(handle, i);
-      DCHECK(!Dart_IsError(element));
-      result.append(DartConverter<T>::FromDart(element));
+      Dart_Handle item = Dart_ListGetAt(handle, i);
+      DCHECK(!Dart_IsError(item));
+      DCHECK(item);
+      result.append(DartConverter<T>::FromDart(item));
     }
     return result;
   }
 
   static Vector<T> FromArguments(Dart_NativeArguments args,
                                  int index,
                                  Dart_Handle& exception,
                                  bool auto_scope = true) {
     // TODO(abarth): What should we do with auto_scope?
     return FromDart(Dart_GetNativeArgument(args, index));
@@ skipping 58 matching lines @@
 
 
 // Alias Dart_NewStringFromCString for less typing.
 inline Dart_Handle ToDart(const char* val) {
   return Dart_NewStringFromCString(val);
 }
 
 }  // namespace blink
 
 #endif  // SKY_ENGINE_TONIC_DART_CONVERTER_H_