Support requesting subsets of host permissions using the permissions API.

chrome/common/extensions/permissions/permission_set.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/permissions/permission_set.h"
 
 #include <algorithm>
 #include <iterator>
 #include <string>
 
@@ skipping 206 matching lines @@
 }
 
 bool PermissionSet::operator==(
     const PermissionSet& rhs) const {
   return apis_ == rhs.apis_ &&
       scriptable_hosts_ == rhs.scriptable_hosts_ &&
       explicit_hosts_ == rhs.explicit_hosts_;
 }
 
 bool PermissionSet::Contains(const PermissionSet& set) const {
-  // Every set includes the empty set.
-  if (set.IsEmpty())
-    return true;
-
-  if (!apis_.Contains(set.apis()))
-      return false;
-
-  if (!explicit_hosts().Contains(set.explicit_hosts()))
-    return false;
-
-  if (!scriptable_hosts().Contains(set.scriptable_hosts()))
-    return false;
-
-  return true;
+  return apis_.Contains(set.apis()) &&
+         explicit_hosts().Contains(set.explicit_hosts()) &&
+         scriptable_hosts().Contains(set.scriptable_hosts());
 }
 
 std::set<std::string> PermissionSet::GetAPIsAsStrings() const {
   std::set<std::string> apis_str;
   for (APIPermissionSet::const_iterator i = apis_.begin();
        i != apis_.end(); ++i) {
     apis_str.insert(i->name());
   }
   return apis_str;
 }
@@ skipping 360 matching lines @@
   std::set<std::string> new_hosts_only;
 
   std::set_difference(new_hosts_set.begin(), new_hosts_set.end(),
                       old_hosts_set.begin(), old_hosts_set.end(),
                       std::inserter(new_hosts_only, new_hosts_only.begin()));
 
   return !new_hosts_only.empty();
 }
 
 }  // namespace extensions