Support web workers in dart2js.

sdk/lib/_internal/compiler/implementation/lib/js_helper.dart

Index: sdk/lib/_internal/compiler/implementation/lib/js_helper.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/lib/js_helper.dart	(revision 16103)
+++ sdk/lib/_internal/compiler/implementation/lib/js_helper.dart	(working copy)
@@ -1117,13 +1117,18 @@
   if (closure == null) return null;
   var function = JS('var', r'#.$identity', closure);
   if (JS('bool', r'!!#', function)) return function;
+  // Fetch the current isolate in a local variable to prevent the
+  // compiler from inlining its use in the following JS expression:
+  // the current isolate may have changed so if we read it from the JS
+  // closure, it leads to the wrong isolate.
+  var currentIsolate = JS_CURRENT_ISOLATE();
 
   function = JS("var", r"""function() {

[ahe, 2012/12/14 08:33:31]

Why doesn't this function take two arguments?

[ahe, 2012/12/14 08:33:31]

I think it would be cleaner if this expression was moved to its own function,
like this:

function = buildJsClosure(DART_CLOSURE_TO_JS(invokeClosure),
    closure,
    JS_CURRENT_ISOLATE(),
    arity);

buildJsClosure(jsInvokeClosure, closure, currentIsolate, arity) {
  return JS('var' ,'function(a, b) { return #(#, #, #, a, b); }',
      jsInvokeClosure, closure, currentIsolate, arity);
}

[ngeoffray, 2012/12/14 09:13:16]

That's a good question. I'll address it in a different CL.

     return #(#, #, #, arguments[0], arguments[1]);
   }""",
   DART_CLOSURE_TO_JS(invokeClosure),

[ahe, 2012/12/14 08:33:31]

Weird indentation.

   closure,
-  JS_CURRENT_ISOLATE(),
+  currentIsolate,
   arity);
 
   JS('void', r'#.$identity = #', closure, function);