Add ignore-unrecognized-flags as an option to the command line options of analysis server

pkg/analyzer/lib/options.dart

Index: pkg/analyzer/lib/options.dart
diff --git a/pkg/analyzer/lib/options.dart b/pkg/analyzer/lib/options.dart
index 50519dcfcc18409c41aba31340e972094c6d9528..9d9b5810f3ac12979232968b01434ff524c98389 100644
--- a/pkg/analyzer/lib/options.dart
+++ b/pkg/analyzer/lib/options.dart
@@ -133,7 +133,7 @@ class CommandLineOptions {
 
   static CommandLineOptions _parse(List<String> args) {
     args = args.expand((String arg) => arg.split('=')).toList();
-    var parser = new _CommandLineParser()
+    var parser = new CommandLineParser()
         ..addFlag(
             'batch',
             abbr: 'b',
@@ -208,8 +208,7 @@ class CommandLineOptions {
         ..addOption(
             'url-mapping',
             help: '--url-mapping=libraryUri,/path/to/library.dart directs the '
-                  'analyzer to use "library.dart" as the source for an import '
-                  'of "libraryUri"',
+                'analyzer to use "library.dart" as the source for an import ' 'of "libraryUri"',
             allowMultiple: true)
         //
         // Hidden flags.
@@ -282,7 +281,9 @@ class CommandLineOptions {
         customUrlMappings[splitMapping[0]] = splitMapping[1];
       }
       return new CommandLineOptions._fromArgs(
-          results, definedVariables, customUrlMappings);
+          results,
+          definedVariables,
+          customUrlMappings);
     } on FormatException catch (e) {
       print(e.message);
       _showUsage(parser);
@@ -305,17 +306,19 @@ class CommandLineOptions {
  * TODO(pquitslund): when the args package supports ignoring unrecognized
  * options/flags, this class can be replaced with a simple [ArgParser] instance.
  */
-class _CommandLineParser {
+class CommandLineParser {
 
   final List<String> _knownFlags;
   final ArgParser _parser;
 
   /** Creates a new command line parser */
-  _CommandLineParser()
+  CommandLineParser()
       : _knownFlags = <String>[],
         _parser = new ArgParser(allowTrailingOptions: true);
 
 
+  ArgParser get parser => _parser;
+
   /**
    * Defines a flag.
    *