Add preliminary support for methods to AstBuilder.

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 6100785b2b196c036231b78d5da75c53a2d9c70b..8be392c3981576b243f47ca736359b1031082413 100644
--- a/pkg/front_end/lib/src/fasta/parser/listener.dart
+++ b/pkg/front_end/lib/src/fasta/parser/listener.dart
@@ -452,6 +452,16 @@ class Listener {
 
   void beginMethod(Token token, Token name) {}
 
+  /// Handle the end of a method declaration.  Substructures:
+  /// - metadata
+  /// - modifiers
+  /// - return type
+  /// - method name (identifier, possibly qualified)
+  /// - type variables
+  /// - formal parameters
+  /// - initializers
+  /// - async marker
+  /// - body
   void endMethod(Token getOrSet, Token beginToken, Token endToken) {
     logEvent("Method");
   }