remove node.js dependency by running the frog compiler in

tools/testing/frogpad/frogpad.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // Copyright (c) 2012, 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.
 
 /**
  * This is the entrypoint for a version of the frog compiler that 
  * can run in the browser.
  * Because this is running in the browser, frog cannot access
  * the file system.  Instead, we assume the all necessary files
  * have been placed in inert <script> elements somewhere on the page.  
  * (See frogpad.py for more details on how the html page is constructed.)
  */
 
 #import("dart:html", prefix:"html");
 #import("../../../frog/lang.dart");
 #import("../../../frog/file_system.dart");
 
 // id of script element containing name of the main dart file
 // to compile.
 final String MAIN_ID = "main_id";
 
 void main() {
   String warnings = "";
   HtmlFileSystem fs = new HtmlFileSystem();
   String mainFile = getText(MAIN_ID); 
   setText("input", fs.readAll(mainFile));
 
   int time1 = new Date.now().value;
-  List<String> args = ["dummy_arg1", "dummy_arg2", mainFile];
+  List<String> args = [
+      "dummy_arg1",
+      "dummy_arg2",
+      "--enable_type_checks",
+      "--enable_asserts",
+    mainFile];
   parseOptions("dummy_home_dir", args, fs);
 
   options.useColors = false;
 
   initializeWorld(fs);
   world.messageHandler = void _(
       String prefix, String message, SourceSpan span) {
     String location = "";
     if (span !== null) {
       location = span.locationText;
     }
     warnings += prefix + message + location + "\n";
   };
   bool success = world.compile();
   int time2 = new Date.now().value;
-  String output = world.getGeneratedCode();
+  String output = "throw 'frogpad compilation error';\n";
   if (success) {
-    setText("output", output);
+    output = world.getGeneratedCode();
   }
+  setText("output", output);
   setText("warnings", warnings);
 
   ((time2 - time1) / 1000).toStringAsPrecision(3);
   String timing = "generated ${output.length} characters in " + 
       "${((time2 - time1) / 1000).toStringAsPrecision(3)} seconds";
   setText("timing", timing);
 }
 
 void setText(String id, String text) {
   html.Element element = html.document.query("#$id");
@@ skipping 73 matching lines @@
   }
 
   void createDirectory(String path, [bool recursive]) {
     throw new UnsupportedOperationException("");
   }
   
   void removeDirectory(String path, [bool recursive]) {
     throw new UnsupportedOperationException("");
   }
 }