Enable conditional directives by default.

pkg/analyzer_cli/lib/src/options.dart

Index: pkg/analyzer_cli/lib/src/options.dart
diff --git a/pkg/analyzer_cli/lib/src/options.dart b/pkg/analyzer_cli/lib/src/options.dart
index 4bf126d24cfd15f63ae9ce62ad2578115e582d8c..3c2e4f56fbc776217eddd4107fced11ac3db4e4a 100644
--- a/pkg/analyzer_cli/lib/src/options.dart
+++ b/pkg/analyzer_cli/lib/src/options.dart
@@ -80,9 +80,6 @@ class CommandLineOptions {
   /// Whether to display version information
   final bool displayVersion;
 
-  /// Whether to enable conditional directives (DEP 40).
-  final bool enableConditionalDirectives;
-
   /// Whether to enable null-aware operators (DEP 9).
   final bool enableNullAwareOperators;
 
@@ -163,7 +160,6 @@ class CommandLineOptions {
         analysisOptionsFile = args['options'],
         disableHints = args['no-hints'],
         displayVersion = args['version'],
-        enableConditionalDirectives = args['enable-conditional-directives'],
         enableNullAwareOperators = args['enable-null-aware-operators'],
         enableStrictCallChecks = args['enable-strict-call-checks'],
         enableSuperMixins = args['supermixin'],