Revert "cleanup unused incremental resolution"

pkg/front_end/lib/src/scanner/token.dart

Index: pkg/front_end/lib/src/scanner/token.dart
diff --git a/pkg/front_end/lib/src/scanner/token.dart b/pkg/front_end/lib/src/scanner/token.dart
index ca3ea2b47d982f0e80fbc336c4c8349fe4cbfb53..b1be439cb668b22e2b6d2a210236322ecc7acd94 100644
--- a/pkg/front_end/lib/src/scanner/token.dart
+++ b/pkg/front_end/lib/src/scanner/token.dart
@@ -84,6 +84,16 @@ class BeginTokenWithComment extends BeginToken implements TokenWithComment {
     _setCommentParent(_precedingComment);
   }
 
+  @override
+  void applyDelta(int delta) {
+    super.applyDelta(delta);
+    Token token = precedingComments;
+    while (token != null) {
+      token.applyDelta(delta);
+      token = token.next;
+    }
+  }
+
   @override
   Token copy() =>
       new BeginTokenWithComment(type, offset, copyComments(precedingComments));
@@ -479,6 +489,16 @@ class KeywordTokenWithComment extends KeywordToken implements TokenWithComment {
     _setCommentParent(_precedingComment);
   }
 
+  @override
+  void applyDelta(int delta) {
+    super.applyDelta(delta);
+    Token token = precedingComments;
+    while (token != null) {
+      token.applyDelta(delta);
+      token = token.next;
+    }
+  }
+
   @override
   Token copy() => new KeywordTokenWithComment(
       keyword, offset, copyComments(precedingComments));
@@ -561,6 +581,11 @@ class SimpleToken implements Token {
   @override
   String get stringValue => type.stringValue;
 
+  @override
+  void applyDelta(int delta) {
+    offset += delta;
+  }
+
   @override
   Token copy() => new Token(type, offset);
 
@@ -678,6 +703,16 @@ class StringTokenWithComment extends StringToken implements TokenWithComment {
     _setCommentParent(_precedingComment);
   }
 
+  @override
+  void applyDelta(int delta) {
+    super.applyDelta(delta);
+    Token token = precedingComments;
+    while (token != null) {
+      token.applyDelta(delta);
+      token = token.next;
+    }
+  }
+
   @override
   Token copy() => new StringTokenWithComment(
       type, lexeme, offset, copyComments(precedingComments));
@@ -860,6 +895,11 @@ abstract class Token implements SyntacticEntity {
    */
   TokenType get type;
 
+  /**
+   * Apply (add) the given [delta] to this token's offset.
+   */
+  void applyDelta(int delta);
+
   /**
    * Return a newly created token that is a copy of this tokens
    * including any [preceedingComment] tokens,