Reduce the expected number of categorized libraries in Dart SDK

Author: srawlins

tool/task.dart

@@ -937,8 +937,8 @@ Not all files are formatted:
 Future<void> validateSdkDocs() async {
   await docSdk();
   const expectedLibCount = 0;
-  const expectedSubLibCounts = {19, 20, 21};
-  const expectedTotalCounts = {19, 20, 21};
+  const expectedSubLibCount = 13;
+  const expectedTotalCount = 20;
   var indexHtml = File(path.join(_sdkDocsDir.path, 'index.html'));
   if (!indexHtml.existsSync()) {
     throw StateError("No 'index.html' found for the SDK docs");
@@ -955,8 +955,8 @@ Future<void> validateSdkDocs() async {
 
   var foundSubLibCount =
       _findCount(indexContents, '<li class="section-subitem"><a href="dart-');
-  if (!expectedSubLibCounts.contains(foundSubLibCount)) {
-    throw StateError("Expected $expectedSubLibCounts 'dart:' entries in "
+  if (expectedSubLibCount != foundSubLibCount) {
+    throw StateError("Expected $expectedSubLibCount 'dart:' entries in "
         "'index.html' to be in categories, but found $foundSubLibCount");
   }
   print('$foundSubLibCount index.html dart: entries in categories found');
@@ -965,11 +965,11 @@ Future<void> validateSdkDocs() async {
   var libraries =
       _sdkDocsDir.listSync().where((fs) => fs.path.contains('dart-'));
   var libraryCount = libraries.length;
-  if (!expectedTotalCounts.contains(libraryCount)) {
+  if (expectedTotalCount != libraryCount) {
     var libraryNames =
         libraries.map((l) => "'${path.basename(l.path)}'").join(', ');
     throw StateError('Unexpected docs generated for SDK libraries; expected '
-        '$expectedTotalCounts directories, but $libraryCount directories were '
+        '$expectedTotalCount directories, but $libraryCount directories were '
         'generated: $libraryNames');
   }
   print("Found $libraryCount 'dart:' libraries");