Run dart2js tests unmodified in browser.

dart/lib/compiler/implementation/js_backend/emitter.dart

 // 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.
 
 /**
  * A function element that represents a closure call. The signature is copied
  * from the given element.
  */
 class ClosureInvocationElement extends FunctionElement {
   ClosureInvocationElement(SourceString name,
@@ skipping 1197 matching lines @@
     Element main = compiler.mainApp.find(Compiler.MAIN);
     String mainCall = null;
     if (compiler.isolateLibrary != null) {
       Element isolateMain =
         compiler.isolateLibrary.find(Compiler.START_ROOT_ISOLATE);
       mainCall = buildIsolateSetup(buffer, main, isolateMain);
     } else {
       mainCall = '${namer.isolateAccess(main)}()';
     }
     buffer.add("""
-if (typeof document != 'undefined' && document.readyState != 'complete') {
+if (typeof dartMainRunner == 'function') {

[kasperl, 2012/09/06 10:29:29]

Somehow it feels shaky to not wait until the document has loaded if the
dartMainRunner hook has been set. Would it be possible to simply wrap the
mainCall in dartMainRunner if it is set instead but keep the document.readyState
logic?

[ahe, 2012/09/08 13:32:32]

Done.

+  dartMainRunner(function() { ${mainCall}; });
+} else if (typeof document != 'undefined' && document.readyState != 'complete') {
   document.addEventListener('readystatechange', function () {
     if (document.readyState == 'complete') {
       ${mainCall};
     }
   }, false);
 } else {
   ${mainCall};
 }
 """);
   }
@@ skipping 68 matching lines @@
         sourceName = token.slowToString();
       }
       int totalOffset = bufferOffset + offset;
       sourceMapBuilder.addMapping(
           sourceFile, token.charOffset, sourceName, totalOffset);
     });
   }
 }
 
 typedef void DefineMemberFunction(String invocationName, CodeBuffer definition);