New verbose flag for the dart command line analyzer

pkg/analyzer/lib/src/analyzer_impl.dart

Index: pkg/analyzer/lib/src/analyzer_impl.dart
diff --git a/pkg/analyzer/lib/src/analyzer_impl.dart b/pkg/analyzer/lib/src/analyzer_impl.dart
index a107ef293ff041af7e09b9dba859a09f9d3aa9ef..f50d41266e5d4aafa1832b5ecd68523f1d98dc8e 100644
--- a/pkg/analyzer/lib/src/analyzer_impl.dart
+++ b/pkg/analyzer/lib/src/analyzer_impl.dart
@@ -159,7 +159,9 @@ class AnalyzerImpl {
     context = AnalysisEngine.instance.createAnalysisContext();
     context.sourceFactory = sourceFactory;
     // Uncomment the following to have errors reported on stdout and stderr
-//    AnalysisEngine.instance.logger = new StdLogger();
+    if (options.verbose) {
+      AnalysisEngine.instance.logger = new StdLogger();
+    }
 
     // set options for context
     AnalysisOptionsImpl contextOptions = new AnalysisOptionsImpl();