partially implement instance of checks and some codegen fixes

lib/runtime/dart/isolate.js

Index: lib/runtime/dart/isolate.js
diff --git a/lib/runtime/dart/isolate.js b/lib/runtime/dart/isolate.js
index b215271447ac7e3642f645452424e4100eaa5358..c5a509a390c9c143146aff040f83c4d55e1418ab 100644
--- a/lib/runtime/dart/isolate.js
+++ b/lib/runtime/dart/isolate.js
@@ -34,7 +34,7 @@ var isolate;
         return dart.as(_isolate_helper.IsolateNatives.spawnFunction(entryPoint, message, paused).then(dart.closureWrap((msg) => new Isolate(dart.as(dart.dindex(msg, 1), SendPort), {pauseCapability: dart.as(dart.dindex(msg, 2), Capability), terminateCapability: dart.as(dart.dindex(msg, 3), Capability)}), "(List<dynamic>) → dynamic")), async.Future$(Isolate));
       } catch (e) {
         let st = dart.stackTrace(e);
-        return new async.Future.error(e, st);
+        return new async.Future$(Isolate).error(e, st);
       }
 
     }
@@ -56,7 +56,7 @@ var isolate;
         return dart.as(_isolate_helper.IsolateNatives.spawnUri(uri, args, message, paused).then(dart.closureWrap((msg) => new Isolate(dart.as(dart.dindex(msg, 1), SendPort), {pauseCapability: dart.as(dart.dindex(msg, 2), Capability), terminateCapability: dart.as(dart.dindex(msg, 3), Capability)}), "(List<dynamic>) → dynamic")), async.Future$(Isolate));
       } catch (e) {
         let st = dart.stackTrace(e);
-        return new async.Future.error(e, st);
+        return new async.Future$(Isolate).error(e, st);
       }
 
     }