Allow manifest handlers to declare keys they depend on that must be parsed before them.

chrome/common/extensions/manifest_tests/extension_manifests_launch_unittest.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/common/extensions/manifest_tests/extension_manifest_test.h"
 
 #include "base/command_line.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/extensions/extension.h"
 #include "chrome/common/extensions/extension_manifest_constants.h"
 #include "extensions/common/error_utils.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace errors = extension_manifest_errors;
+namespace keys = extension_manifest_keys;
 
 using extensions::ErrorUtils;
 
 TEST_F(ExtensionManifestTest, AppLaunchContainer) {
   scoped_refptr<extensions::Extension> extension;
 
   extension = LoadAndExpectSuccess("launch_tab.json");
   EXPECT_EQ(extension_misc::LAUNCH_TAB, extension->launch_container());
 
   extension = LoadAndExpectSuccess("launch_panel.json");
@@ skipping 89 matching lines @@
                          errors::kInvalidLaunchValue,
                          keys::kLaunchWebURL));
 
   extension = LoadAndExpectSuccess("launch_web_url_absolute.json");
   EXPECT_EQ(GURL("http://www.google.com/launch.html"),
             extension->GetFullLaunchURL());
   extension = LoadAndExpectSuccess("launch_web_url_localized.json");
   EXPECT_EQ(GURL("http://www.google.com/launch.html"),
             extension->GetFullLaunchURL());
 }