Clean up the patch file for the isolate library by introducing a new builtin library: isolate_helpe…

sdk/lib/_internal/compiler/implementation/native_handler.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.
 
 library native;
 
 import 'dart:uri';
 import 'dart2jslib.dart' hide SourceString;
 import 'elements/elements.dart';
 import 'js_backend/js_backend.dart';
@@ skipping 434 matching lines @@
         '${unusedClasses.length} native classes omitted.');
   }
 }
 
 void maybeEnableNative(Compiler compiler,
                        LibraryElement library,
                        Uri uri) {
   String libraryName = uri.toString();
   if (library.entryCompilationUnit.script.name.contains(
           'dart/tests/compiler/dart2js_native')
-      || libraryName == 'dart:isolate'
       || libraryName == 'dart:html'
       || libraryName == 'dart:html_common'
       || libraryName == 'dart:indexed_db'
       || libraryName == 'dart:svg'
       || libraryName == 'dart:web_audio') {
     library.canUseNative = true;
   }
 }
 
 /**
@@ skipping 422 matching lines @@
         builder.add(new HForeign(
             new DartString.literal('${parameter.name.slowToString()} = #'),
             const LiteralDartString('void'),
             <HInstruction>[jsClosure]));
       }
     });
     LiteralString jsCode = nativeBody.asLiteralString();
     builder.push(new HForeign.statement(jsCode.dartString, <HInstruction>[]));
   }
 }