Clarify presentation of the target in retaining paths.

runtime/observatory/lib/src/elements/code_view.dart

Index: runtime/observatory/lib/src/elements/code_view.dart
diff --git a/runtime/observatory/lib/src/elements/code_view.dart b/runtime/observatory/lib/src/elements/code_view.dart
index f7e263c32e795e4519772f456c1c36aaaca67442..bbbde907042170029fa46dd21695f2311e4aeb2f 100644
--- a/runtime/observatory/lib/src/elements/code_view.dart
+++ b/runtime/observatory/lib/src/elements/code_view.dart
@@ -644,6 +644,6 @@ class CodeViewElement extends HtmlElement implements Renderable {
       case M.CodeKind.collected:
         return 'collected';
     }
-    throw new Exception('Unkown CodeKind ($kind)');
+    throw new Exception('Unknown CodeKind ($kind)');
   }
 }