Remove unneeded `strong_mode_down_cast_composite` ignores.

pkg/analyzer/tool/summary/mini_ast.dart

 // Copyright (c) 2017, 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.
 
 import 'package:front_end/src/fasta/errors.dart';
 import 'package:front_end/src/fasta/parser/identifier_context.dart';
 import 'package:front_end/src/fasta/parser/parser.dart';
 import 'package:front_end/src/fasta/scanner/token.dart';
 import 'package:front_end/src/fasta/source/stack_listener.dart';
 
@@ skipping 171 matching lines @@
   }
 
   void endClassDeclaration(
       int interfacesCount,
       Token beginToken,
       Token classKeyword,
       Token extendsKeyword,
       Token implementsKeyword,
       Token endToken) {
     debugEvent("ClassDeclaration");
-    // ignore: strong_mode_down_cast_composite
     List<ClassMember> members = pop();
     TypeName superclass = pop();
     pop(); // Type variables
     String name = pop();
-    // ignore: strong_mode_down_cast_composite
     List<Annotation> metadata = pop();
     Comment comment = pop();
     compilationUnit.declarations.add(
         new ClassDeclaration(comment, metadata, name, superclass, members));
   }
 
   @override
   void endCombinators(int count) {
     debugEvent("Combinators");
   }
@@ skipping 11 matching lines @@
       Token start, Token periodBeforeName, Token endToken) {
     debugEvent("ConstructorReference");
     String constructorName = popIfNotNull(periodBeforeName);
     pop(); // Type arguments
     String name = pop();
     push(new ConstructorReference(name, constructorName));
   }
 
   void endEnum(Token enumKeyword, Token endBrace, int count) {
     debugEvent("Enum");
-    // ignore: strong_mode_down_cast_composite
     List<EnumConstantDeclaration> constants = popList(count);
     String name = pop();
-    // ignore: strong_mode_down_cast_composite
     List<Annotation> metadata = pop();
     Comment comment = pop();
     compilationUnit.declarations
         .add(new EnumDeclaration(comment, metadata, name, constants));
   }
 
   @override
   void endFactoryMethod(
       Token beginToken, Token factoryKeyword, Token endToken) {
     debugEvent("FactoryMethod");
     pop(); // Body
     ConstructorReference name = pop();
-    // ignore: strong_mode_down_cast_composite
     List<Annotation> metadata = pop();
     Comment comment = pop();
     push(new ConstructorDeclaration(comment, metadata, name));
   }
 
   @override
   void endFieldInitializer(Token assignment) {
     debugEvent("FieldInitializer");
     pop(); // Expression
   }
@@ skipping 46 matching lines @@
 
   @override
   void endMember() {
     debugEvent("Member");
   }
 
   @override
   void endMetadata(Token beginToken, Token periodBeforeName, Token endToken) {
     debugEvent("Metadata");
     inMetadata = false;
-    // ignore: strong_mode_down_cast_composite
     List<Expression> arguments = pop();
     String constructorName = popIfNotNull(periodBeforeName);
     pop(); // Type arguments
     String name = pop();
     push(new Annotation(name, constructorName, arguments));
   }
 
   @override
   void endMetadataStar(int count, bool forParameter) {
     debugEvent("MetadataStar");
     push(popList(count) ?? NullValue.Metadata);
   }
 
   void endMethod(Token getOrSet, Token beginToken, Token endToken) {
     debugEvent("Method");
     pop(); // Body
     pop(); // Initializers
     pop(); // Formal parameters
     pop(); // Type variables
     String name = pop();
     TypeName returnType = pop();
-    // ignore: strong_mode_down_cast_composite
     List<Annotation> metadata = pop();
     Comment comment = pop();
     push(new MethodDeclaration(
         comment, metadata, getOrSet?.lexeme == 'get', name, returnType));
   }
 
   @override
   void endSend(Token beginToken, Token endToken) {
     debugEvent("Send");
-    // ignore: strong_mode_down_cast_composite
     pop(); // Arguments
     pop(); // Type arguments
     pop(); // Receiver
     push(new UnknownExpression());
   }
 
   @override
   void endShow(Token showKeyword) {
     debugEvent("Show");
     pop(); // Shown names
@@ skipping 73 matching lines @@
   void handleQualified(Token period) {
     debugEvent("Qualified");
     String suffix = pop();
     String prefix = pop();
     push('$prefix.$suffix');
   }
 
   @override
   void handleType(Token beginToken, Token endToken) {
     debugEvent("Type");
-    // ignore: strong_mode_down_cast_composite
     List<TypeName> typeArguments = pop();
     String name = pop();
     push(new TypeName(name, typeArguments));
   }
 }
 
 /// Parser intended for use with [MiniAstBuilder].
 class MiniAstParser extends Parser {
   MiniAstParser(MiniAstBuilder listener) : super(listener);
 
@@ skipping 23 matching lines @@
   final String name;
 
   final List<TypeName> typeArguments;
 
   TypeName(this.name, this.typeArguments);
 }
 
 /// "Mini AST" representation of an expression which summary code generation
 /// need not be concerned about.
 class UnknownExpression extends Expression {}