[Blink-Workers]Set verbosity of the external exception handler.

third_party/WebKit/LayoutTests/fast/workers/resources/onerror-test.js

 function stripURL(url) {
     if (url.match(/^blob:/))
         return "[blob: URL]";
     return url ? url.match( /[^\/]+\/?$/ )[0] : url;
 }
 
 function checkErrorEvent(errorEvent, obj) {
     window.errorEvent = errorEvent;
     shouldBeEqualToString('errorEvent.message', obj.message);
     shouldBeEqualToString('stripURL(errorEvent.filename)', obj.filename);
@@ skipping 51 matching lines @@
     });
 }
 
 function errorEventHandlerShouldNotFire() {
     var worker = buildInlineWorker();
     worker.onerror = function (e) {
         testFailed("'worker.onerror' should not have been called.");
     };
 }
 
+function errorEventHandlerShouldFire() {
+    var worker = buildInlineWorker();
+    worker.onerror = function (e) {
+        testPassed("'worker.onerror' called.");
+    };
+}
+
 function buildInlineWorker() {
     var script = document.getElementById('workerCode').innerText;
     var blob = new Blob([script], {type: 'text/javascript'});
     var worker = new Worker(URL.createObjectURL(blob));
 
     if (window.postMessageCallback)
         worker.addEventListener('message', postMessageCallback);
     worker.addEventListener('message', function (e) {
         if (e.data.done)
             return finishJSTest();
     });
 
     return worker;
 }
 
 window.jsTestIsAsync = true;