Fixed ExtensionApiTest.Bookmarks and enabled it again.

chrome/browser/bookmarks/bookmark_extension_api.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/bookmarks/bookmark_extension_api.h"
 
 #include "base/bind.h"
 #include "base/file_path.h"
 #include "base/i18n/file_util_icu.h"
 #include "base/i18n/time_formatting.h"
@@ skipping 486 matching lines @@
       error_ = keys::kInvalidIndexError;
       return false;
     }
   }
 
   string16 title;
   json->GetString(keys::kTitleKey, &title);  // Optional.
   std::string url_string;
   json->GetString(keys::kUrlKey, &url_string);  // Optional.
   GURL url(url_string);
-  if (!url.is_empty() && !url.is_valid()) {
+  if (!url_string.empty() && !url.is_valid()) {
     error_ = keys::kInvalidUrlError;
     return false;
   }
 
   const BookmarkNode* node;
   if (url_string.length())
     node = model->AddURL(parent, index, title, url);
   else
     node = model->AddFolder(parent, index, title);
   DCHECK(node);
@@ skipping 427 matching lines @@
                                            int index,
                                            void* params) {
 #if !defined(OS_ANDROID)
   // Android does not have support for the standard exporter.
   // TODO(jgreenwald): remove ifdef once extensions are no longer built on
   // Android.
   bookmark_html_writer::WriteBookmarks(profile(), path, NULL);
 #endif
   Release();  // Balanced in BookmarksIOFunction::SelectFile()
 }