Add support for SDK outline in KernelDriver.

pkg/front_end/lib/src/incremental/file_state.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 'dart:convert';
 import 'dart:typed_data';
 
 import 'package:convert/convert.dart';
 import 'package:crypto/crypto.dart';
@@ skipping 263 matching lines @@
   _FileSystemView _fileSystemView;
 
   /// Mapping from import URIs to corresponding [FileState]s. For example, this
   /// may contain an entry for `dart:core`.
   final Map<Uri, FileState> _uriToFile = {};
 
   /// Mapping from file URIs to corresponding [FileState]s. This map should only
   /// contain `file:*` URIs as keys.
   final Map<Uri, FileState> _fileUriToFile = {};
 
+  /// The set of absolute URIs with the `dart` scheme that should be skipped.
+  /// We do this when we use SDK outline instead of compiling SDK sources.
+  final Set<Uri> skipSdkLibraries = new Set<Uri>();
+
   FileSystemState(this._byteStore, this.fileSystem, this.uriTranslator,
       this._salt, this._newFileFn);
 
   /// Return the [FileSystem] that is backed by this [FileSystemState].  The
   /// files in this [FileSystem] always have the same content as the
   /// corresponding [FileState]s, thus avoiding race conditions when a file
   /// is updated on the actual file system.
   FileSystem get fileSystemView {
     return _fileSystemView ??= new _FileSystemView(this);
   }
@@ skipping 32 matching lines @@
     urisToRemove.forEach(_uriToFile.remove);
     fileUrisToRemove.forEach(_fileUriToFile.remove);
     return filesToRemove;
   }
 
   /// Return the [FileState] for the given [absoluteUri], or `null` if the
   /// [absoluteUri] cannot be resolved into a file URI.
   ///
   /// The returned file has the last known state since it was last refreshed.
   Future<FileState> getFile(Uri absoluteUri) async {
+    // We don't need to process SDK libraries if we have SDK outline.
+    if (skipSdkLibraries.contains(absoluteUri)) {
+      return null;
+    }
+
     // Resolve the absolute URI into the absolute file URI.
     Uri fileUri;
     if (absoluteUri.isScheme('file')) {
       fileUri = absoluteUri;
     } else {
       fileUri = uriTranslator.translate(absoluteUri);
       if (fileUri == null) return null;
     }
 
     FileState file = _uriToFile[absoluteUri];
@@ skipping 165 matching lines @@
       cycle.libraries.add(node.file);
       fileToCycleMap[node.file] = cycle;
     }
     topologicallySortedCycles.add(cycle);
   }
 
   _LibraryNode getNode(FileState file) {
     return nodesOfFiles.putIfAbsent(file, () => new _LibraryNode(this, file));
   }
 }