Add KernelWorldBuilder and KElement model.

pkg/compiler/lib/src/kernel/element_adapter.dart

 // Copyright (c) 2017, 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.
 
 import 'package:kernel/ast.dart' as ir;
 
 import '../common.dart';
 import '../common/names.dart';
 import '../core_types.dart';
 import '../elements/elements.dart';
@@ skipping 122 matching lines @@
     List<String> namedArguments = arguments.named.map((e) => e.name).toList();
     return new CallStructure(argumentCount, namedArguments);
   }
 
   @override
   Selector getSelector(ir.Expression node) {
     if (node is ir.PropertyGet) return getGetterSelector(node);
     if (node is ir.PropertySet) return getSetterSelector(node);
     if (node is ir.InvocationExpression) return getInvocationSelector(node);
     throw new SpannableAssertionFailure(CURRENT_ELEMENT_SPANNABLE,
-        "Can only get the selector for a property get or an invocation: ${node}");
+        "Can only get the selector for a property get or an invocation: "
+        "${node}");
   }
 
   Selector getInvocationSelector(ir.InvocationExpression invocation) {
     Name name = getName(invocation.name);
     SelectorKind kind;
     if (Elements.isOperatorName(invocation.name.name)) {
       if (name == Names.INDEX_NAME || name == Names.INDEX_SET_NAME) {
         kind = SelectorKind.INDEX;
       } else {
         kind = SelectorKind.OPERATOR;
@@ skipping 213 matching lines @@
   String visitStringConcatenation(ir.StringConcatenation node) {
     StringBuffer sb = new StringBuffer();
     for (ir.Expression expression in node.expressions) {
       String value = expression.accept(this);
       if (value == null) return null;
       sb.write(value);
     }
     return sb.toString();
   }
 }