Clean up hacky handling of "dart:" URIs in incremental resolved AST generator.

pkg/front_end/lib/src/incremental_resolved_ast_generator_impl.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:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/context/context.dart';
 import 'package:analyzer/src/dart/analysis/byte_store.dart';
@@ skipping 56 matching lines @@
     // should be eliminated ASAP.
     var graph =
         await graphForProgram([_source], _options, fileReader: _fileReader);
     // TODO(paulberry): collect no-longer-referenced files from _fileState and
     // _fileRepository.
     var libraries = <Uri, ResolvedLibrary>{};
     if (!_schedulerStarted) {
       _scheduler.start();
       _schedulerStarted = true;
     }
-    // The driver will request files from dart:, even though it actually uses
-    // the data from the summary.  TODO(paulberry): fix this.
-    _fileRepository.store(Uri.parse('dart:core'), '');
     for (var libraryCycle in graph.topologicallySortedCycles) {
       for (var libraryUri in libraryCycle.libraries.keys) {
         var libraryNode = libraryCycle.libraries[libraryUri];
         for (var partUri in libraryNode.parts) {
           // TODO(paulberry): resolve the part URI.
           _fileReader(partUri, partUri);
         }
       }
       for (var libraryUri in libraryCycle.libraries.keys) {
         var libraryNode = libraryCycle.libraries[libraryUri];
@@ skipping 25 matching lines @@
     // TODO(paulberry): can we just use null?
     var performanceLog = new driver.PerformanceLog(new _NullStringSink());
     _scheduler = new driver.AnalysisDriverScheduler(performanceLog);
     _resourceProvider = new _ResourceProviderProxy(_fileRepository);
     // TODO(paulberry): MemoryByteStore leaks memory (it never discards data).
     // Do something better here.
     var byteStore = new MemoryByteStore();
     // TODO(paulberry): can we just use null?
     var fileContentOverlay = new FileContentOverlay();
     var sdkContext = new AnalysisContextImpl();
-    var dartSdk = new _DartSdkProxy(await _options.getSdkSummary(), sdkContext);
+    var dartSdk = new _DartSdkProxy(
+        await _options.getSdkSummary(), sdkContext, _fileRepository);
     sdkContext.sourceFactory =
         new SourceFactory([new DartUriResolver(dartSdk)]);
     bool strongMode = true; // TODO(paulberry): support strong mode flag.
     sdkContext.resultProvider = new SdkSummaryResultProvider(
         sdkContext, await _options.getSdkSummary(), strongMode);
 
     var sourceFactory = new _SourceFactoryProxy(dartSdk, _fileRepository);
     var analysisOptions = new AnalysisOptionsImpl();
     _driver = new driver.AnalysisDriver(
         _scheduler,
@@ skipping 29 matching lines @@
     _fileRepository.store(originalUri, contents);
     return contents;
   }
 }
 
 class _DartSdkProxy implements DartSdk {
   final PackageBundle summary;
 
   final AnalysisContext context;
 
-  _DartSdkProxy(this.summary, this.context);
+  final FileRepository _fileRepository;
+
+  _DartSdkProxy(this.summary, this.context, this._fileRepository);
 
   @override
   PackageBundle getLinkedBundle() => summary;
 
   @override
-  Source mapDartUri(String uri) {
-    // TODO(paulberry): this seems hacky.
-    return new _SourceProxy(Uri.parse(uri), '$uri.dart');
+  Source mapDartUri(String uriString) {
+    var uri = Uri.parse(uriString);
+    return new _SourceProxy(
+        uri, _fileRepository.pathForUri(uri, allocate: true));
   }
 
   noSuchMethod(Invocation invocation) => unimplemented();
 }
 
 class _FileProxy implements File {
   final _SourceProxy _source;
 
   final _ResourceProviderProxy _resourceProvider;
 
@@ skipping 96 matching lines @@
 class _SourceProxy extends BasicSource {
   @override
   final String fullName;
 
   _SourceProxy(Uri uri, this.fullName) : super(uri);
 
   int get modificationStamp => 0;
 
   noSuchMethod(Invocation invocation) => unimplemented();
 }