Replace factory constructor with a static method for creating IncrementalKernelGenerator.

pkg/front_end/lib/src/incremental_kernel_generator_impl.dart

Index: pkg/front_end/lib/src/incremental_kernel_generator_impl.dart
diff --git a/pkg/front_end/lib/src/incremental_kernel_generator_impl.dart b/pkg/front_end/lib/src/incremental_kernel_generator_impl.dart
index 780852dfcb62b80e3885e65c1718588d0996fb9e..c19ed2adb848f614a596db84367d2c7ace247170 100644
--- a/pkg/front_end/lib/src/incremental_kernel_generator_impl.dart
+++ b/pkg/front_end/lib/src/incremental_kernel_generator_impl.dart
@@ -29,32 +29,33 @@ dynamic unimplemented() {
 /// used to obtain resolved ASTs, and these are fed into kernel code generation
 /// logic.
 class IncrementalKernelGeneratorImpl implements IncrementalKernelGenerator {
-  /// The URI of the program entry point.
-  final Uri _entryPoint;
-
   /// The compiler options, such as the [FileSystem], the SDK dill location,
   /// etc.
   final ProcessedOptions _options;
 
-  /// The set of absolute file URIs that were reported through [invalidate]
-  /// and not checked for actual changes yet.
-  final Set<Uri> _invalidatedFiles = new Set<Uri>();
-
   /// The object that knows how to resolve "package:" and "dart:" URIs.
-  TranslateUri _uriTranslator;
+  final TranslateUri _uriTranslator;
 
   /// The current file system state.
-  FileSystemState _fsState;
+  final FileSystemState _fsState;
+
+  /// The URI of the program entry point.
+  final Uri _entryPoint;
+
+  /// The set of absolute file URIs that were reported through [invalidate]
+  /// and not checked for actual changes yet.
+  final Set<Uri> _invalidatedFiles = new Set<Uri>();
 
   /// The cached SDK kernel.
   DillTarget _sdkDillTarget;
 
-  IncrementalKernelGeneratorImpl(this._entryPoint, this._options);
+  IncrementalKernelGeneratorImpl(
+      this._options, this._uriTranslator, this._entryPoint)
+      : _fsState = new FileSystemState(_options.fileSystem, _uriTranslator);
 
   @override
   Future<DeltaProgram> computeDelta(
       {Future<Null> watch(Uri uri, bool used)}) async {
-    await _initialize();
     await _ensureVmLibrariesLoaded();
     await _refreshInvalidatedFiles();
 
@@ -115,15 +116,6 @@ class IncrementalKernelGeneratorImpl implements IncrementalKernelGenerator {
     return _sdkDillTarget;
   }
 
-  /// Ensure that asynchronous data from options is ready.
-  ///
-  /// Ideally this data should be prepared in the constructor, but constructors
-  /// cannot be asynchronous.
-  Future<Null> _initialize() async {
-    _uriTranslator ??= await _options.getUriTranslator();
-    _fsState ??= new FileSystemState(_options.fileSystem, _uriTranslator);
-  }
-
   /// Refresh all the invalidated files and update dependencies.
   Future<Null> _refreshInvalidatedFiles() async {
     for (Uri fileUri in _invalidatedFiles) {