Change accessors and AstFactory to use tokens rather than file offsets.

pkg/front_end/lib/src/fasta/kernel/kernel_ast_factory.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/scanner/token.dart'
+    show Token, offsetForToken;
 import 'package:kernel/ast.dart';
 
 import '../builder/ast_factory.dart';
 import 'kernel_shadow_ast.dart';
 
 /// Concrete implementation of [builder.AstFactory] for building a kernel AST.
 class KernelAstFactory implements AstFactory {
   @override
-  KernelBlock block(List<Statement> statements, int charOffset) {
-    return new KernelBlock(statements)..fileOffset = charOffset;
+  KernelBlock block(List<Statement> statements, Token beginToken) {
+    return new KernelBlock(statements)..fileOffset = offsetForToken(beginToken);
   }
 
   @override
   Field field(Name name, int charOffset, {String fileUri}) {
     return new KernelField(name, fileUri: fileUri)..fileOffset = charOffset;
   }
 
   @override
-  KernelIntLiteral intLiteral(value, int charOffset) {
-    return new KernelIntLiteral(value)..fileOffset = charOffset;
+  KernelIntLiteral intLiteral(value, Token token) {
+    return new KernelIntLiteral(value)..fileOffset = offsetForToken(token);
   }
 
   @override
   KernelListLiteral listLiteral(List<Expression> expressions,
-      DartType typeArgument, bool isConst, int charOffset) {
+      DartType typeArgument, bool isConst, Token token) {
     return new KernelListLiteral(expressions,
         typeArgument: typeArgument, isConst: isConst)
-      ..fileOffset = charOffset;
+      ..fileOffset = offsetForToken(token);
   }
 
   @override
-  KernelNullLiteral nullLiteral(int charOffset) {
-    return new KernelNullLiteral()..fileOffset = charOffset;
+  KernelNullLiteral nullLiteral(Token token) {
+    return new KernelNullLiteral()..fileOffset = offsetForToken(token);
   }
 
   @override
-  KernelReturnStatement returnStatement(Expression expression, int charOffset) {
-    return new KernelReturnStatement(expression)..fileOffset = charOffset;
+  KernelReturnStatement returnStatement(Expression expression, Token token) {
+    return new KernelReturnStatement(expression)
+      ..fileOffset = offsetForToken(token);
   }
 
   @override
-  StaticGet staticGet(Member readTarget, int offset) {
-    return new KernelStaticGet(readTarget)..fileOffset = offset;
+  StaticGet staticGet(Member readTarget, Token token) {
+    return new KernelStaticGet(readTarget)..fileOffset = offsetForToken(token);
   }
 
   @override
-  KernelVariableDeclaration variableDeclaration(String name, int charOffset,
+  KernelVariableDeclaration variableDeclaration(String name, Token token,
       {DartType type,
       Expression initializer,
-      int equalsCharOffset = TreeNode.noOffset,
+      Token equalsToken,
       bool isFinal: false,
       bool isConst: false}) {
     return new KernelVariableDeclaration(name,
         type: type,
         initializer: initializer,
         isFinal: isFinal,
         isConst: isConst)
-      ..fileOffset = charOffset
-      ..fileEqualsOffset = equalsCharOffset;
+      ..fileOffset = offsetForToken(token)
+      ..fileEqualsOffset = offsetForToken(equalsToken);
   }
 }