Make it so that chrome.bookmarks.update can update the URL of a bookmark....

chrome/test/data/extensions/api_test/bookmarks/test.js

 // bookmarks api test
 // browser_tests.exe --gtest_filter=ExtensionApiTest.Bookmarks
 
 var expected = [
   {"children": [
       {children:[], id:"1", parentId:"0", index:0, title:"Bookmarks bar"},
       {children:[], id:"2", parentId:"0", index:1, title:"Other bookmarks"}
     ],
    id:"0", title:""
   }
@@ skipping 250 matching lines @@
   },
 
   function update() {
     var title = "hello world";
     chrome.test.listenOnce(chrome.bookmarks.onChanged, function(id, changes) {
       chrome.test.assertEq(title, changes.title);
     });
     chrome.bookmarks.update(node1.id, {"title": title}, pass(function(results) {
       chrome.test.assertEq(title, results.title);
     }));
+
+    var url = "http://example.com/hello"
+    chrome.bookmarks.update(node1.id, {"url": url}, pass(function(results) {
+      // Make sure that leaving out the title does not set the title to empty.
+      chrome.test.assertEq(title, results.title);
+      chrome.test.assertEq(url, results.url);
+    }));
   },
 
   function remove() {
     var parentId = node1.parentId;
     chrome.test.listenOnce(chrome.bookmarks.onRemoved,
                            function(id, removeInfo) {
       chrome.test.assertEq(id, node1.id);
       chrome.test.assertEq(removeInfo.parentId, parentId);
       chrome.test.assertEq(removeInfo.index, node1.index);
     });
@@ skipping 117 matching lines @@
 
     chrome.bookmarks.getRecent(2, pass(function(results) {
       chrome.test.assertEq(2, results.length,
                            "Should only get the last 2 bookmarks");
 
       chrome.test.assertTrue(compareNode(node3, results[0]));
       chrome.test.assertTrue(compareNode(node2, results[1]));
     }));
   }
 ]);