Add @overrides to (a lot of) analyzer.

pkg/analyzer/lib/src/dart/ast/token.dart

Index: pkg/analyzer/lib/src/dart/ast/token.dart
diff --git a/pkg/analyzer/lib/src/dart/ast/token.dart b/pkg/analyzer/lib/src/dart/ast/token.dart
index 02d28e5ec2edd54ec0e6b7819ba1c37d0e4795db..1791990e53cfb54a65be3b44962e2eea0281a9e5 100644
--- a/pkg/analyzer/lib/src/dart/ast/token.dart
+++ b/pkg/analyzer/lib/src/dart/ast/token.dart
@@ -39,6 +39,7 @@ class BeginTokenWithComment extends BeginToken implements TokenWithComment {
   /**
    * The first comment in the list of comments that precede this token.
    */
+  @override
   CommentToken _precedingComment;
 
   /**
@@ -54,6 +55,7 @@ class BeginTokenWithComment extends BeginToken implements TokenWithComment {
   @override
   CommentToken get precedingComments => _precedingComment;
 
+  @override
   void set precedingComments(CommentToken comment) {
     _precedingComment = comment;
     _setCommentParent(_precedingComment);
@@ -168,6 +170,7 @@ class KeywordTokenWithComment extends KeywordToken implements TokenWithComment {
   /**
    * The first comment in the list of comments that precede this token.
    */
+  @override
   CommentToken _precedingComment;
 
   /**