Correctly indent the RHS of 'is' and 'as' expressions.

lib/src/source_visitor.dart

 // Copyright (c) 2014, 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 dart_style.src.source_visitor;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/src/generated/source.dart';
 
@@ skipping 141 matching lines @@
       _visitCollectionLiteral(
           null, node.leftParenthesis, node.arguments, node.rightParenthesis);
       return;
     }
 
     new ArgumentListVisitor(this, node).visit();
   }
 
   visitAsExpression(AsExpression node) {
     builder.startSpan();
+    builder.nestExpression();
     visit(node.expression);
     soloSplit();
     token(node.asOperator);
     space();
     visit(node.type);
+    builder.unnest();
     builder.endSpan();
   }
 
   // TODO(rnystrom): Type annotate once analyzer publishes a version with the
   // new AST type.
   // TODO(rnystrom): Test.
   visitAssertInitializer(node) {
     _simpleStatement(node, () {
       token(node.assertKeyword);
 
@@ skipping 1056 matching lines @@
     visit(node.expression);
     token(node.rightBracket);
   }
 
   visitInterpolationString(InterpolationString node) {
     token(node.contents);
   }
 
   visitIsExpression(IsExpression node) {
     builder.startSpan();
+    builder.nestExpression();
     visit(node.expression);
     soloSplit();
     token(node.isOperator);
     token(node.notOperator);
     space();
     visit(node.type);
+    builder.unnest();
     builder.endSpan();
   }
 
   visitLabel(Label node) {
     visit(node.label);
     token(node.colon);
   }
 
   visitLabeledStatement(LabeledStatement node) {
     _visitLabels(node.labels);
@@ skipping 1331 matching lines @@
   /// Gets the 1-based line number that the beginning of [token] lies on.
   int _startLine(Token token) => _lineInfo.getLocation(token.offset).lineNumber;
 
   /// Gets the 1-based line number that the end of [token] lies on.
   int _endLine(Token token) => _lineInfo.getLocation(token.end).lineNumber;
 
   /// Gets the 1-based column number that the beginning of [token] lies on.
   int _startColumn(Token token) =>
       _lineInfo.getLocation(token.offset).columnNumber;
 }