Rewrite the 'window.onerror' tests.

LayoutTests/fast/events/resources/onerror-test.js

+function stripURL(url) {
+    return url ? url.match( /[^\/]+\/?$/ )[0] : url;
+}
+
+function throwException(message) {
+    throw new Error(message ? message : "An exception");
+}
+
+var errorsSeen = 0;
+function DumpOnErrorArgumentValuesAndReturn(returnValue, callback) {

[do-not-use, 2013/07/24 13:18:01]

nit: function usually start with a lowercase in Blink (unlike Chromium).

[Mike West, 2013/07/24 15:28:32]

Done.

+    window.onerror = function (message, url, line, column) {
+        debug("window.onerror: \"" + message + "\" at " + stripURL(url) + " (" + line + ", " + column + ")");

[do-not-use, 2013/07/24 13:18:01]

nit: I find the output in expected results not very readable for the value in
the parenthesis. Maybe we could add "line:" / "column:" before them to clarify?

[Mike West, 2013/07/24 15:28:32]

Done.

+
+        if (callback)
+            callback(++errorsSeen);
+        if (returnValue)
+            debug("- Returning 'true': the error should not be reported in the console as an unhandled exception.");

[do-not-use, 2013/07/24 13:18:01]

I think we can remove the "- " prefix, I don't find it makes the output more
readable.

[Mike West, 2013/07/24 15:28:32]

Done.

+        else
+            debug("- Returning 'false': the error should be reported in the console as an unhandled exception.");
+        return returnValue;
+    };
+}
+
+function DumpErrorEventAndAllowDefault(callback) {

[do-not-use, 2013/07/24 13:18:01]

Ditto.

[Mike West, 2013/07/24 15:28:32]

Done.

+    window.addEventListener('error', function (e) {
+        DumpErrorEvent(e)
+        debug("- Not calling e.preventDefault(): the error should be reported in the console as an unhandled exception.");
+        if (callback)
+            callback(++errorsSeen);
+    });
+}
+
+function DumpErrorEventAndPreventDefault(callback) {

[do-not-use, 2013/07/24 13:18:01]

ditto.

[Mike West, 2013/07/24 15:28:32]

Done.

+    window.addEventListener('error', function (e) {
+        DumpErrorEvent(e);
+        debug("- Calling e.preventDefault(): the error should not be reported in the console as an unhandled exception.");
+        e.preventDefault();
+        if (callback)
+            callback(++errorsSeen);
+    });
+}
+
+var eventPassedToTheErrorListener = null;
+var eventCurrentTarget = null;
+function DumpErrorEvent(e) {

[do-not-use, 2013/07/24 13:18:01]

Ditto.

[Mike West, 2013/07/24 15:28:32]

Done.

+    debug("Handling '" + e.type + "' event (phase " + e.eventPhase + "): \"" + e.message + "\" at " + stripURL(e.filename) + ":" + e.lineno);
+
+    eventPassedToTheErrorListener = e;
+    eventCurrentTarget = e.currentTarget;
+    shouldBe('eventPassedToTheErrorListener', 'window.event');
+    shouldBe('eventCurrentTarget', 'window');
+    eventPassedToTheErrorListener = null;
+    eventCurrentTarget = null;
+}