Re-land minor tweaks to the analyzer cli's usage text.

pkg/analyzer/lib/src/command_line/arguments.dart

Index: pkg/analyzer/lib/src/command_line/arguments.dart
diff --git a/pkg/analyzer/lib/src/command_line/arguments.dart b/pkg/analyzer/lib/src/command_line/arguments.dart
index f120ad0ea025b0b362aba2f912373de6a0727e48..467b71f591f2002ff99785512729b38e3d236a78 100644
--- a/pkg/analyzer/lib/src/command_line/arguments.dart
+++ b/pkg/analyzer/lib/src/command_line/arguments.dart
@@ -173,7 +173,7 @@ void defineAnalysisArguments(ArgParser parser, {bool hide: true, ddc: false}) {
   parser.addFlag(enableInitializingFormalAccessFlag,
       help:
           'Enable support for allowing access to field formal parameters in a '
-          'constructor\'s initializer list',
+          'constructor\'s initializer list.',
       defaultsTo: false,
       negatable: false,
       hide: hide || ddc);