Convert DartChangeBuilder to use AnalysisSession

pkg/analysis_server/lib/src/services/completion/postfix/postfix_completion.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 'dart:async';
 
 import 'package:analysis_server/src/protocol_server.dart' hide Element;
 import 'package:analysis_server/src/services/correction/util.dart';
+import 'package:analyzer/dart/analysis/session.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/error/error.dart' as engine;
 import 'package:analyzer/src/dart/analysis/driver.dart';
 import 'package:analyzer/src/dart/ast/utilities.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/java_core.dart';
 import 'package:analyzer/src/generated/resolver.dart';
 import 'package:analyzer/src/generated/source.dart';
@@ skipping 280 matching lines @@
   String get file => completionContext.file;
 
   String get key => completionContext.key;
 
   LineInfo get lineInfo => completionContext.lineInfo;
 
   int get requestLine => lineInfo.getLocation(selectionOffset).lineNumber;
 
   int get selectionOffset => completionContext.selectionOffset;
 
+  /**
+   * Return the analysis session to be used to create the change builder.
+   */
+  AnalysisSession get session => driver.currentSession;
+
   Source get source => completionContext.unitElement.source;
 
   TypeProvider get typeProvider {
     return _typeProvider ??= unitElement.context.typeProvider;
   }
 
   CompilationUnit get unit => completionContext.unit;
 
   CompilationUnitElement get unitElement => completionContext.unitElement;
 
   Future<PostfixCompletion> compute() async {
     node = _selectedNode();
     if (node == null) {
       return NO_COMPLETION;
     }
     PostfixCompletionKind completer = DartPostfixCompletion.forKey(key);
     return completer?.computer(this, completer) ?? NO_COMPLETION;
   }
 
   Future<PostfixCompletion> expand(
       PostfixCompletionKind kind, Function contexter, Function sourcer,
       {bool withBraces: true}) async {
     AstNode expr = contexter();
     if (expr == null) {
       return null;
     }
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(driver);
+    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addReplacement(range.node(expr), (DartEditBuilder builder) {
         String newSrc = sourcer(expr);
         if (newSrc == null) {
           return null;
         }
         builder.write(newSrc);
         if (withBraces) {
           builder.write(" {");
           builder.write(eol);
@@ skipping 13 matching lines @@
     return completion;
   }
 
   Future<PostfixCompletion> expandTry(
       PostfixCompletionKind kind, Function contexter,
       {bool withOn: false}) async {
     AstNode stmt = contexter();
     if (stmt == null) {
       return null;
     }
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(driver);
+    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       // Embed the full line(s) of the statement in the try block.
       var startLine = lineInfo.getLocation(stmt.offset).lineNumber - 1;
       var endLine = lineInfo.getLocation(stmt.end).lineNumber - 1;
       if (stmt is ExpressionStatement && !stmt.semicolon.isSynthetic) {
         endLine += 1;
       }
       var startOffset = lineInfo.getOffsetOfLine(startLine);
       var endOffset = lineInfo.getOffsetOfLine(endLine);
       var src = utils.getText(startOffset, endOffset - startOffset);
@@ skipping 174 matching lines @@
       [List args]) {
     SourceChange change = builder.sourceChange;
     if (change.edits.isEmpty) {
       completion = null;
       return;
     }
     change.message = formatList(kind.message, args);
     completion = new PostfixCompletion(kind, change);
   }
 }