Implement API features for the Extension API feature system

chrome/common/extensions/features/permission_feature.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/features/permission_feature.h"
 
 #include "chrome/common/extensions/permissions/permission_set.h"
 
 namespace extensions {
 
@@ skipping 18 matching lines @@
   // Optional permissions need to be checked so an API will not be set to
   // undefined forever, when it could just need optional permissions.
   if (extension && !extension->HasAPIPermission(name()) &&
       !extension->optional_permission_set()->HasAnyAccessToAPI(name())) {
     return CreateAvailability(NOT_PRESENT, extension->GetType());
   }
 
   return CreateAvailability(IS_AVAILABLE);
 }
 
+std::string PermissionFeature::Parse(const DictionaryValue* value) {
+  std::string error = SimpleFeature::Parse(value);
+  if (!error.empty())
+    return error;
+
+  if (extension_types()->empty()) {
+    return name() + ": Permission features must specify at least one " +
+        "value for extension_types.";
+  }
+
+  if (!GetContexts()->empty())
+    return name() + ": Permission features do not support contexts.";
+
+  return "";
+}
+
 }  // namespace