auto merge of #1666 : ozten/servo/issue-506-add-basic-console, r=Ms2ger

Here is an attempt to fix Issue#506.

I couldn't figure out how to do variadic arguments to `console.log`, but I did test calling `console.log('foo', 'bar', 'baz')` and it prints the first argument and doesn't error out, which is nice.

window.console is not a web standards. I did the popular functions, but not some of the newer ones documented [on MDN](https://developer.mozilla.org/en-US/docs/Web/API/console).

This PR will allow more pages to load properly, where developers have left in window.console calls.

src/components/script/dom/webidls/Console.webidl

@@ -0,0 +1,20 @@
+/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * References:
+ *   MDN Docs - https://developer.mozilla.org/en-US/docs/Web/API/console
+ *   Draft Spec - http://sideshowbarker.github.io/console-spec/
+ *
+ * © Copyright 2014 Mozilla Foundation.
+ */
+
+interface Console {
+  // These should be DOMString message, DOMString message2, ...
+  void log(DOMString message);
+  void debug(DOMString message);
+  void info(DOMString message);
+  void warn(DOMString message);
+  void error(DOMString message);
+};

src/components/script/dom/webidls/Window.webidl

@@ -55,6 +55,13 @@
 
 
 };
+
+// Not part of any spec
+partial interface Window {
+  // web developer niceties
+  readonly attribute Console console;
+};
+
 /*Window implements GlobalEventHandlers;
   Window implements WindowEventHandlers;*/