Fix several failing tests

pkg/analyzer/lib/src/fasta/ast_builder.dart

 // Copyright (c) 2016, 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 fasta.analyzer.ast_builder;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/dart/ast/ast_factory.dart' show AstFactory;
 import 'package:analyzer/dart/ast/standard_ast_factory.dart' as standard;
 import 'package:analyzer/dart/ast/token.dart' show Token, TokenType;
@@ skipping 1208 matching lines @@
         whileKeyword,
         condition.leftParenthesis,
         condition.expression,
         condition.rightParenthesis,
         semicolon));
   }
 
   void endConditionalUri(Token ifKeyword, Token equalitySign) {
     debugEvent("ConditionalUri");
     StringLiteral libraryUri = pop();
-    // TODO(paulberry,ahe): the parser should report the right paren token to
-    // the listener.
-    Token rightParen = null;
     StringLiteral value;
     if (equalitySign != null) {
       value = pop();
     }
     DottedName name = pop();
     // TODO(paulberry,ahe): what if there is no `(` token due to an error in the
     // file being parsed?  It seems like we need the parser to do adequate error
     // recovery and then report both the ifKeyword and leftParen tokens to the
     // listener.
     Token leftParen = ifKeyword.next;
+    // TODO(paulberry,ahe): the parser should report the right paren token to
+    // the listener.

[danrubel, 2017/08/30 17:44:03]

Is this comment still valid? Are there situations in which `rightParen` is not
')' ?

[Brian Wilkerson, 2017/08/30 18:03:49]

I think so...

If the paren is missing, or if there are tokens between the name and the paren
that are discarded during recovery, we'll get the wrong token here. This code
should probably check the token type and set `rightParen` to null to help catch
that case. But in order to get it right, the listener really needs the parser to
send it *all* of the tokens rather than having any of them inferred by location.

+    Token rightParen = name.endToken.next;
     push(ast.configuration(ifKeyword, leftParen, name, equalitySign, value,
         rightParen, libraryUri));
   }
 
   @override
   void endConditionalUris(int count) {
     debugEvent("ConditionalUris");
     push(popList(count) ?? NullValue.ConditionalUris);
   }
 
@@ skipping 803 matching lines @@
       } else if (identical('var', s)) {
         finalConstOrVarKeyword = token;
       } else if (identical('covariant', s)) {
         covariantKeyword = token;
       } else {
         unhandled("$s", "modifier", token.charOffset, null);
       }
     }
   }
 }