Clear old messages when reporting exception.

dart/site/try/src/compilation.dart

Index: dart/site/try/src/compilation.dart
diff --git a/dart/site/try/src/compilation.dart b/dart/site/try/src/compilation.dart
index 0fcc7937089ab020dd17cb61b6574183475fd45c..4b4a61a38eef3ddc3e5deac577ed947d2dcc76ad 100644
--- a/dart/site/try/src/compilation.dart
+++ b/dart/site/try/src/compilation.dart
@@ -197,6 +197,7 @@ self.importScripts("$url");
 
   void run(String url, IFrameElement makeIframe()) {
     void retryInIframe() {
+      interaction.aboutToRun();
       var frame = makeIframe();
       frame.style
           ..visibility = 'hidden'
@@ -206,9 +207,8 @@ self.importScripts("$url");
       errorStream(frame).listen(interaction.onIframeError);
     }
     void onError(String errorMessage) {
+      interaction.consolePrintLine(errorMessage);
       console
-          ..appendText(errorMessage)
-          ..appendText(' ')
           ..append(buildButton('Try in iframe', (_) => retryInIframe()))
           ..appendText('\n');
     }