Add ability to limit when context menu items appear with url patterns....

chrome/test/data/extensions/context_menus/simple/test.js

Index: chrome/test/data/extensions/context_menus/simple/test.js
===================================================================
--- chrome/test/data/extensions/context_menus/simple/test.js	(revision 0)
+++ chrome/test/data/extensions/context_menus/simple/test.js	(working copy)
@@ -25,8 +25,8 @@
 }
 
 window.onload = function() {
-  chrome.experimental.contextMenus.create({"title":"Extension Item 1",
-                                          "onclick": onclick}, function(id) {
+  chrome.contextMenus.create({"title":"Extension Item 1",
+                              "onclick": onclick}, function() {
     if (!chrome.extension.lastError) {
       navigateCurrentTab(chrome.extension.getURL("test.html"));
     }