Refactor Library/CompilationUnit and how we define local Scope.

lib/compiler/implementation/scanner/class_element_parser.dart

 // Copyright (c) 2011, 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.
 
 class ClassElementParser extends PartialParser {
   ClassElementParser(Listener listener) : super(listener);
 
   Token parseClassBody(Token token) => fullParseClassBody(token);
 }
 
 class PartialClassElement extends ClassElement {
   final Token beginToken;
   final Token endToken;
   Node cachedNode;
 
   PartialClassElement(SourceString name,
                       Token this.beginToken,
                       Token this.endToken,
-                      CompilationUnitElement enclosing,
+                      Element enclosing,
                       int id)
     : super(name, enclosing, id);
 
   ClassNode parseNode(DiagnosticListener diagnosticListener) {
     if (cachedNode != null) return cachedNode;
     MemberListener listener = new MemberListener(diagnosticListener, this);
     Parser parser = new ClassElementParser(listener);
     Token token = parser.parseTopLevelDeclaration(beginToken);
     assert(token === endToken.next);
     cachedNode = listener.popNode();
@@ skipping 99 matching lines @@
   }
 
   void endInitializers(int count, Token beginToken, Token endToken) {
     pushNode(null);
   }
 
   void addMember(Element memberElement) {
     enclosingElement.addMember(memberElement, listener);
   }
 }