Add 'error' parameter to 'window.onerror' handlers.

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) {
-    window.onerror = function (message, url, line, column) {
+    window.onerror = function (message, url, line, column, error) {
         debug("window.onerror: \"" + message + "\" at " + stripURL(url) + " (Line: " + line + ", Column: " + column + ")");
+        if (error)
+            debug(stripStackURLs(error.stack));
 
         if (callback)
             callback(++errorsSeen);
         if (returnValue)
             debug("Returning 'true': the error should not be reported in the console as an unhandled exception.");
         else
             debug("Returning 'false': the error should be reported in the console as an unhandled exception.");
         return returnValue;
     };
 }
@@ skipping 14 matching lines @@
         e.preventDefault();
         if (callback)
             callback(++errorsSeen);
     });
 }
 
 var eventPassedToTheErrorListener = null;
 var eventCurrentTarget = null;
 function dumpErrorEvent(e) {
     debug("Handling '" + e.type + "' event (phase " + e.eventPhase + "): \"" + e.message + "\" at " + stripURL(e.filename) + ":" + e.lineno);
+    if (e.error)
+        debug(stripStackURLs(e.error.stack));
 
     eventPassedToTheErrorListener = e;
     eventCurrentTarget = e.currentTarget;
     shouldBe('eventPassedToTheErrorListener', 'window.event');
     shouldBe('eventCurrentTarget', 'window');
     eventPassedToTheErrorListener = null;
     eventCurrentTarget = null;
 }
+
+function stripStackURLs(stackTrace) {
+    var text = stackTrace + "\n\n";
+    stackTrace = stackTrace.split("\n");
+    var length = Math.min(stackTrace.length, 100);
+    for (var i = 0; i < length; i++) {
+        text += stackTrace[i].replace(/at ((?:eval at \()?[a-zA-Z\.]+ )?\(?.+\/([^\/]+):(\d+):(\d+)\)?/, "at $1$2:$3:$4") + "\n";
+    }
+    return text;
+}