Print the first compile-time error in console.

dart/site/try/src/compilation.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library trydart.compilation;
 
 import 'dart:html' show
     Blob,
     Element,
     ErrorEvent,
@@ skipping 60 matching lines @@
 
 class CompilationProcess {
   final String source;
   final Element console;
   final ReceivePort receivePort = new ReceivePort();
   final Set<String> seenMessages = new Set<String>();
   bool isDone = false;
   bool usesDartHtml = false;
   Worker worker;
   List<String> objectUrls = <String>[];
+  String firstError;
 
   static CompilationProcess current;
 
   CompilationProcess(this.source, this.console);
 
   static bool shouldStartCompilation() {
     if (compilerPort == null) return false;
     if (isMalformedInput) return false;
     if (current != null) return current.isDone;
     return true;
@@ skipping 41 matching lines @@
       default:
         throw ['Unknown message kind', message];
     }
   }
 
   onDartHtml(_) {
     usesDartHtml = true;
   }
 
   onFail(_) {
-    interaction.onCompilationFailed();
+    interaction.onCompilationFailed(firstError);
   }
 
   onDone(_) {
     interaction.onCompilationDone();
     isDone = true;
     receivePort.close();
   }
 
   // This is called in browsers that support creating Object URLs in a
   // web worker.  For example, Chrome and Firefox 21.
@@ skipping 80 matching lines @@
   }
 
   onDiagnostic(Map<String, dynamic> diagnostic) {
     if (currentSource != source) return;
     String kind = diagnostic['kind'];
     String message = diagnostic['message'];
     if (kind == 'verbose info') {
       interaction.verboseCompilerMessage(message);
       return;
     }
+    if (kind == 'error' && firstError == null) {
+      firstError = message;
+    }
     String uri = diagnostic['uri'];
     if (uri != '${PRIVATE_SCHEME}:/main.dart') {
       interaction.consolePrintLine('$uri: [$kind] $message');
       return;
     }
     int begin = diagnostic['begin'];
     int end = diagnostic['end'];
     if (begin == null) return;
     if (seenMessages.add('$begin:$end: [$kind] $message')) {
       // Guard against duplicated messages.
       addDiagnostic(kind, message, begin, end);
     }
   }
 
   onCrash(data) {
     interaction.onCompilerCrash(data);
   }
 }