Fix some issues with options handling

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 7e8b9cbb5269cfad824d05dfdab572fdaf7e034d..2e4a3f6bee84ce57ff5f9ee2d941ec9d7c2c89c0 100644
--- a/pkg/analyzer_cli/lib/src/options.dart
+++ b/pkg/analyzer_cli/lib/src/options.dart
@@ -225,6 +225,14 @@ class CommandLineOptions {
   String get packageRootPath =>
       contextBuilderOptions.defaultPackagesDirectoryPath;
 
+  /// The source files to analyze
+  List<String> get sourceFiles => _sourceFiles;
+
+  /// Replace the sourceFiles parsed from the command line.
+  void rewriteSourceFiles(List<String> newSourceFiles) {
+    _sourceFiles = newSourceFiles;
+  }
+
   /// Parse [args] into [CommandLineOptions] describing the specified
   /// analyzer options. In case of a format error, calls [printAndFail], which
   /// by default prints an error message to stderr and exits.
@@ -294,14 +302,6 @@ class CommandLineOptions {
     return options;
   }
 
-  /// The source files to analyze
-  List<String> get sourceFiles => _sourceFiles;
-
-  /// Replace the sourceFiles parsed from the command line.
-  void rewriteSourceFiles(List<String> newSourceFiles) {
-    _sourceFiles = newSourceFiles;
-  }
-
   static String _getVersion() {
     try {
       // This is relative to bin/snapshot, so ../..
@@ -484,7 +484,7 @@ class CommandLineOptions {
           hide: hide)
       ..addFlag('enable-assert-initializers',
           help: 'Enable parsing of asserts in constructor initializers.',
-          defaultsTo: false,
+          defaultsTo: null,
           negatable: false,
           hide: hide)
       ..addFlag('use-analysis-driver-memory-byte-store',