Revert "Start using FileState/FileSystemState to provide consistent view."

pkg/front_end/lib/incremental_kernel_generator.dart

Index: pkg/front_end/lib/incremental_kernel_generator.dart
diff --git a/pkg/front_end/lib/incremental_kernel_generator.dart b/pkg/front_end/lib/incremental_kernel_generator.dart
index f842f9fd9ab68b09fa2f61667ffa667c2849869f..f1094f1e46d937e456c20fa20fde8b22d42edd3c 100644
--- a/pkg/front_end/lib/incremental_kernel_generator.dart
+++ b/pkg/front_end/lib/incremental_kernel_generator.dart
@@ -95,10 +95,12 @@ abstract class IncrementalKernelGenerator {
   /// errors, it is safe to call [computeDelta] again.
   Future<DeltaProgram> computeDelta({Future<Null> watch(Uri uri, bool used)});
 
-  /// Remove the file associated with the given file [uri] from the set of
-  /// valid files.  This guarantees that those files will be re-read on the
+  /// Remove any source file(s) associated with the given file path from the set
+  /// of valid sources.  This guarantees that those files will be re-read on the
   /// next call to [computeDelta]).
-  void invalidate(Uri uri);
+  ///
+  /// TODO(scheglov) Update to use URI.
+  void invalidate(String path);
 
   /// Remove all source files from the set of valid sources.  This guarantees
   /// that all files will be re-read on the next call to [computeDelta].