Fix fetch-canvas-tainting.html to not mix up origins and transferables.

The signature of Window's postMessage is message, target origin,
transferables; not message, transferables, target origin.

https://html.spec.whatwg.org/multipage/comms.html#dom-window-postmessage

BUG=

Review URL: https://codereview.chromium.org/651603004

git-svn-id: svn://svn.chromium.org/blink/trunk@184230 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/LayoutTests/http/tests/serviceworker/fetch-canvas-tainting.html

@@ -34,8 +34,8 @@ async_test(function(t) {
                   service_worker_unregister_and_done(t, SCOPE);
                 });
               frame.contentWindow.postMessage({},
-                                              [channel.port2],
-                                              host_info['HTTP_ORIGIN']);
+                                              host_info['HTTP_ORIGIN'],
+                                              [channel.port2]);
             });
         })
       .catch(unreached_rejection(t));