Add AstBuilder support for DottedName and ConditionalUri.

pkg/front_end/lib/src/fasta/parser/listener.dart

Index: pkg/front_end/lib/src/fasta/parser/listener.dart
diff --git a/pkg/front_end/lib/src/fasta/parser/listener.dart b/pkg/front_end/lib/src/fasta/parser/listener.dart
index 6fd0adda9e8af1c0fa5aa95de066b6764d3b0244..138e4e49b3115e3976e2f4d8792b9fdcfc25906d 100644
--- a/pkg/front_end/lib/src/fasta/parser/listener.dart
+++ b/pkg/front_end/lib/src/fasta/parser/listener.dart
@@ -330,6 +330,10 @@ class Listener {
 
   void beginConditionalUri(Token ifKeyword) {}
 
+  /// Handle the end of a conditional URI construct.  Substructures:
+  /// - Dotted name
+  /// - Condition (literal string; only present if [equalitySign is not `null`)

[scheglov, 2017/02/21 21:32:14]

[equalitySign]

[Paul Berry, 2017/02/21 21:37:37]

Done.

+  /// - URI (literal string)
   void endConditionalUri(Token ifKeyword, Token equalitySign) {
     logEvent("ConditionalUri");
   }