Add 'self.onerror' to Worker tests.

LayoutTests/http/tests/workers/worker-importScripts-onerror-sameorigin.html

Index: LayoutTests/http/tests/workers/worker-importScripts-onerror-sameorigin.html
diff --git a/LayoutTests/http/tests/workers/worker-importScripts-onerror-sameorigin.html b/LayoutTests/http/tests/workers/worker-importScripts-onerror-sameorigin.html
index e1a412aadf20288ac08e2d7712bd76c010c126dd..e7a1ea03a1c7d8dbab7f7ef49080dda05e27954f 100644
--- a/LayoutTests/http/tests/workers/worker-importScripts-onerror-sameorigin.html
+++ b/LayoutTests/http/tests/workers/worker-importScripts-onerror-sameorigin.html
@@ -14,6 +14,15 @@
 
         var worker = new Worker('resources/worker-importscripts-onerror-sameorigin.js');
 
+        var workerOnerror;
+        worker.onmessage = function (e) {
+            workerOnerror = e.data;
+            shouldBeEqualToString("workerOnerror.message", "Uncaught This is a custom error message.");
+            shouldBeEqualToString("workerOnerror.url", "http://127.0.0.1:8000/workers/resources/worker-importscripts-onerror-sameorigin.js");
+            shouldEvaluateTo("workerOnerror.line", 5);
+            shouldEvaluateTo("workerOnerror.column", 0);
+        };
+
         var onerrorMessage, onerrorURL, onerrorLine;
         worker.onerror = function (e) {
             onerrorMessage = e.message;