Stop importing js_helper.dart explicitly in the core library.

lib/compiler/implementation/patch_parser.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.
 
 /**
  * This library contains the infrastructure to parse and integrate patch files.
  *
  * Three types of elements can be patched: [LibraryElement], [ClassElement],
  * [FunctionElement]. Patches are introduced in patch libraries which are loaded
  * together with the corresponding origin library. Which libraries that are
@@ skipping 125 matching lines @@
     LinkBuilder<tree.LibraryTag> imports = new LinkBuilder<tree.LibraryTag>();
     compiler.withCurrentElement(patchLibrary.entryCompilationUnit, () {
       // This patches the elements of the patch library into [library].
       // Injected elements are added directly under the compilation unit.
       // Patch elements are stored on the patched functions or classes.
       scanLibraryElements(patchLibrary.entryCompilationUnit, imports);
     });
     // After scanning declarations, we handle the import tags in the patch.
     // TODO(lrn): These imports end up in the original library and are in
     // scope for the original methods too. This should be fixed.
+    compiler.importHelperLibrary(originLibrary);
     for (tree.LibraryTag tag in imports.toLink()) {
       compiler.scanner.importLibraryFromTag(tag,
                                             patchLibrary.entryCompilationUnit);
     }
   }
 
   void scanLibraryElements(
         CompilationUnitElement compilationUnit,
         LinkBuilder<tree.LibraryTag> imports) {
     measure(() {
@@ skipping 333 matching lines @@
     super.addMember(element);
   }
 }
 
 // TODO(ahe): Get rid of this class.
 class PatchMetadataAnnotation extends MetadataAnnotation {
   final leg.Constant value = null;
 
   PatchMetadataAnnotation() : super(STATE_DONE);
 }