performance measurement improvements and README update

pkg/analysis_server/benchmark/integration/main.dart

Index: pkg/analysis_server/benchmark/integration/main.dart
diff --git a/pkg/analysis_server/benchmark/integration/main.dart b/pkg/analysis_server/benchmark/integration/main.dart
index 979f25659714968e660d86db176e230a481c0573..7cfb299801dc64b5297b1944d7be681bafd139af 100644
--- a/pkg/analysis_server/benchmark/integration/main.dart
+++ b/pkg/analysis_server/benchmark/integration/main.dart
@@ -69,6 +69,43 @@ const TMP_SRC_DIR_OPTION = 'tmpSrcDir';
 const VERBOSE_CMDLINE_OPTION = 'verbose';
 const VERY_VERBOSE_CMDLINE_OPTION = 'vv';
 
+ArgParser _argParser;
+
+ArgParser get argParser {
+  _argParser = new ArgParser();
+
+  _argParser.addOption(INPUT_CMDLINE_OPTION, abbr: 'i', help: '<filePath>\n'
+      'The input file specifying how this client should interact with the server.\n'
+      'If the input file name is "stdin", then the instructions are read from standard input.');
+  _argParser.addOption(MAP_OPTION,
+      abbr: 'm',
+      allowMultiple: true,
+      splitCommas: false,
+      help: '<oldSrcPath>,<newSrcPath>\n'
+          'This option defines a mapping from the original source directory <oldSrcPath>\n'
+          'when the instrumentation or log file was generated\n'
+          'to the target source directory <newSrcPath> used during performance testing.\n'
+          'Multiple mappings can be specified.\n'
+          'WARNING: The contents of the target directory will be modified');
+  _argParser.addOption(TMP_SRC_DIR_OPTION, abbr: 't', help: '<dirPath>\n'
+      'The temporary directory containing source used during performance measurement.\n'
+      'WARNING: The contents of the target directory will be modified');
+  _argParser.addFlag(NEW_TASK_MODEL_OPTION,
+      help: "enable the use of the new task model",
+      defaultsTo: false,
+      negatable: false);
+  _argParser.addOption(DIAGNOSTIC_PORT_OPTION,
+      abbr: 'd',
+      help: 'localhost port on which server will provide diagnostic web pages');
+  _argParser.addFlag(VERBOSE_CMDLINE_OPTION,
+      abbr: 'v', help: 'Verbose logging', negatable: false);
+  _argParser.addFlag(VERY_VERBOSE_CMDLINE_OPTION,
+      help: 'Extra verbose logging', negatable: false);
+  _argParser.addFlag(HELP_CMDLINE_OPTION,
+      abbr: 'h', help: 'Print this help information', negatable: false);
+  return _argParser;
+}
+
 /**
  * Open and return the input stream specifying how this client
  * should interact with the analysis server.
@@ -96,45 +133,13 @@ Stream<Operation> openInput(PerfArgs args) {
  * Parse the command line arguments.
  */
 PerfArgs parseArgs(List<String> rawArgs) {
-  ArgParser parser = new ArgParser();
-
-  parser.addOption(INPUT_CMDLINE_OPTION, abbr: 'i', help: '<filePath>\n'
-      'The input file specifying how this client should interact with the server.\n'
-      'If the input file name is "stdin", then the instructions are read from standard input.');
-  parser.addOption(MAP_OPTION,
-      abbr: 'm',
-      allowMultiple: true,
-      splitCommas: false,
-      help: '<oldSrcPath>,<newSrcPath>\n'
-      'This option defines a mapping from the original source directory <oldSrcPath>\n'
-      'when the instrumentation or log file was generated\n'
-      'to the target source directory <newSrcPath> used during performance testing.\n'
-      'Multiple mappings can be specified.\n'
-      'WARNING: The contents of the target directory will be modified');
-  parser.addOption(TMP_SRC_DIR_OPTION, abbr: 't', help: '<dirPath>\n'
-      'The temporary directory containing source used during performance measurement.\n'
-      'WARNING: The contents of the target directory will be modified');
-  parser.addFlag(NEW_TASK_MODEL_OPTION,
-      help: "enable the use of the new task model",
-      defaultsTo: false,
-      negatable: false);
-  parser.addOption(DIAGNOSTIC_PORT_OPTION,
-      abbr: 'd',
-      help: 'localhost port on which server will provide diagnostic web pages');
-  parser.addFlag(VERBOSE_CMDLINE_OPTION,
-      abbr: 'v', help: 'Verbose logging', negatable: false);
-  parser.addFlag(VERY_VERBOSE_CMDLINE_OPTION,
-      help: 'Extra verbose logging', negatable: false);
-  parser.addFlag(HELP_CMDLINE_OPTION,
-      abbr: 'h', help: 'Print this help information', negatable: false);
-
   ArgResults args;
   PerfArgs perfArgs = new PerfArgs();
   try {
-    args = parser.parse(rawArgs);
+    args = argParser.parse(rawArgs);
   } on Exception catch (e) {
     print(e);
-    printHelp(parser);
+    printHelp();
     exit(1);
   }
 
@@ -189,18 +194,18 @@ PerfArgs parseArgs(List<String> rawArgs) {
   }
 
   if (showHelp) {
-    printHelp(parser);
+    printHelp();
     exit(1);
   }
 
   return perfArgs;
 }
 
-void printHelp(ArgParser parser) {
+void printHelp() {
   print('');
   print('Launch and interact with the AnalysisServer');
   print('');
-  print(parser.usage);
+  print(argParser.usage);
 }
 
 /**