Move scanner out of generated and clean up imports

pkg/analyzer/lib/src/summary/summarize_const_expr.dart

 // Copyright (c) 2016, 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.
 
 library serialization.summarize_const_expr;
 
+import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/src/generated/ast.dart';
-import 'package:analyzer/src/generated/scanner.dart';
 import 'package:analyzer/src/summary/format.dart';
 import 'package:analyzer/src/summary/idl.dart';
 
 /**
  * Serialize the given constructor initializer [node].
  */
 UnlinkedConstructorInitializer serializeConstructorInitializer(
     ConstructorInitializer node,
     UnlinkedConstBuilder serializeConstExpr(Expression expr)) {
   if (node is ConstructorFieldInitializer) {
@@ skipping 344 matching lines @@
           strings.add(element.value);
         } else {
           _serialize((element as InterpolationExpression).expression);
         }
       }
       operations.add(UnlinkedConstOperation.concatenate);
       ints.add(interpolation.elements.length);
     }
   }
 }