Update charted to 0.4.8 and roll

packages/unittest/lib/html_config.dart

Index: packages/unittest/lib/html_config.dart
diff --git a/packages/unittest/lib/html_config.dart b/packages/unittest/lib/html_config.dart
index c472d58d89ff2e1f76844187b2cb326f64cb22cd..dc866a08e1fdc80f482d22070faef42090fdb2ef 100644
--- a/packages/unittest/lib/html_config.dart
+++ b/packages/unittest/lib/html_config.dart
@@ -140,7 +140,7 @@ class HtmlConfiguration extends SimpleConfiguration {
   void onInit() {
     // For Dart internal tests, we want to turn off stack frame
     // filtering, which we do with this meta-header.
-    var meta = querySelector('meta[name="dart.unittest"]');
+    MetaElement meta = querySelector('meta[name="dart.unittest"]');
     filterStacks =
         meta == null ? true : !meta.content.contains('full-stack-traces');
     _installHandlers();