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

chrome/common/extensions/manifest_tests/extension_manifests_background_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 "base/memory/scoped_ptr.h"
 #include "base/values.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/extensions/extension.h"
 #include "chrome/common/extensions/extension_manifest_constants.h"
 #include "chrome/common/extensions/features/base_feature_provider.h"
 #include "chrome/common/extensions/features/feature.h"
 #include "extensions/common/error_utils.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace errors = extension_manifest_errors;
+namespace keys = extension_manifest_keys;
 
 namespace extensions {
 
 TEST_F(ExtensionManifestTest, BackgroundPermission) {
   LoadAndExpectError("background_permission.json",
                      errors::kBackgroundPermissionNeeded);
 }
 
 TEST_F(ExtensionManifestTest, BackgroundScripts) {
   std::string error;
@@ skipping 68 matching lines @@
   EXPECT_TRUE(extension->has_lazy_background_page());
 
   ListValue* permissions = new ListValue();
   permissions->Append(Value::CreateStringValue("webRequest"));
   manifest->Set(keys::kPermissions, permissions);
   LoadAndExpectError(Manifest(manifest.get(), ""),
                      errors::kWebRequestConflictsWithLazyBackground);
 }
 
 }  // namespace extensions