Remove parsed units caching for now.

I see that we leak them when using DAS.
So, lets remove them for now until we can do this safely.

R=brianwilkerson@google.com, paulberry@google.com

Change-Id: Iaf349225c6e338eacb40e82deb5f84dfaa82e48d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/105326
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

pkg/analyzer/lib/src/dart/analysis/file_state.dart

@@ -121,7 +121,6 @@ class FileState {
   List<int> _apiSignature;
 
   UnlinkedUnit2 _unlinked2;
-  CompilationUnit _unitForLinking;
 
   List<FileState> _importedFiles;
   List<FileState> _exportedFiles;
@@ -535,18 +534,6 @@ class FileState {
     return apiSignatureChanged;
   }
 
-  /// If the file has a parsed unit from computing unlinked data, return it.
-  /// Otherwise, parse it afresh now.
-  CompilationUnit takeUnitForLinking() {
-    if (_unitForLinking != null) {
-      var result = _unitForLinking;
-      _unitForLinking = null;
-      return result;
-    } else {
-      return parse();
-    }
-  }
-
   @override
   String toString() => path ?? '<unresolved>';
 
@@ -658,7 +645,6 @@ class FileState {
       bytes = _fsState._byteStore.get(_unlinkedKey);
       if (bytes == null || bytes.isEmpty) {
         CompilationUnit unit = parse();
-        _unitForLinking = unit;
         _fsState._logger.run('Create unlinked for $path', () {
           var unlinkedUnit = serializeAstUnlinked2(unit);
           var definedNames = computeDefinedNames(unit);

pkg/analyzer/lib/src/dart/analysis/library_context.dart

@@ -283,7 +283,7 @@ class LibraryContext {
           var inputUnits = <link2.LinkInputUnit>[];
           for (var file in libraryFile.libraryFiles) {
             var isSynthetic = !file.exists;
-            var unit = file.takeUnitForLinking();
+            var unit = file.parse();
             inputUnits.add(
               link2.LinkInputUnit(file.source, isSynthetic, unit),
             );