Parse type substitution comments /*=T*/ in variable declarations with Fasta.

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 3bfdb81ecdba6022adde59acbf91218858c1e913..bff471fa420003ec2f219c6c6f887ae7299c107c 100644
--- a/pkg/front_end/lib/src/fasta/parser/listener.dart
+++ b/pkg/front_end/lib/src/fasta/parser/listener.dart
@@ -1028,6 +1028,28 @@ class Listener {
     logEvent("Script");
   }
 
+  /// Matches a generic comment type substitution and injects it into the token
+  /// stream before the given [token].
+  Token injectGenericCommentTypeAssign(Token token) {
+    return token;
+  }
+
+  /// Matches a generic comment type parameters or type arguments and injects
+  /// them into the token stream before the given [token].
+  Token injectGenericCommentTypeList(Token token) {
+    return token;
+  }
+
+  /// If the [tokenWithComment] has a type substitution comment /*=T*/, then
+  /// the comment should be scanned into new tokens, and these tokens inserted
+  /// instead of tokens from the [tokenToStartReplacing] to the
+  /// [tokenWithComment]. Returns the first newly inserted token, or the
+  /// original [tokenWithComment].
+  Token replaceTokenWithGenericCommentTypeAssign(
+      Token tokenToStartReplacing, Token tokenWithComment) {
+    return tokenToStartReplacing;
+  }
+
   /// Creates a new synthetic token whose `next` pointer points to [next].
   ///
   /// If [next] is `null`, `null` is returned.