Don't use file-based part-of when part files are shared.

sdk/lib/html/html_common/conversions_dart2js.dart

-part of "html_common.dart";
+part of "html_common_dart2js.dart";
 
 /// Converts a JavaScript object with properties into a Dart Map.
 /// Not suitable for nested objects.
 Map convertNativeToDart_Dictionary(object) {
   if (object == null) return null;
   var dict = {};
   var keys = JS('JSExtendableArray', 'Object.getOwnPropertyNames(#)', object);
   for (final key in keys) {
     dict[key] = JS('var', '#[#]', object, key);
   }
@@ skipping 84 matching lines @@
 
 const String _serializedScriptValue = 'num|String|bool|'
     'JSExtendableArray|=Object|'
     'Blob|File|NativeByteBuffer|NativeTypedData'
     // TODO(sra): Add Date, RegExp.
     ;
 const annotation_Creates_SerializedScriptValue =
     const Creates(_serializedScriptValue);
 const annotation_Returns_SerializedScriptValue =
     const Returns(_serializedScriptValue);