Purge cache when the server removes the policy for an extension.

components/policy/core/common/policy_namespace.h

 // Copyright 2013 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.
 
 #ifndef COMPONENTS_POLICY_CORE_COMMON_POLICY_NAMESPACE_H_
 #define COMPONENTS_POLICY_CORE_COMMON_POLICY_NAMESPACE_H_
 
 #include <string>
 #include <vector>
 
+#include "base/containers/hash_tables.h"
 #include "components/policy/policy_export.h"
 
 namespace policy {
 
 // Policies are namespaced by a (PolicyDomain, ID) pair. The meaning of the ID
 // string depends on the domain; for example, if the PolicyDomain is
 // "extensions" then the ID identifies the extension that the policies control.
 enum POLICY_EXPORT PolicyDomain {
   // The component ID for chrome policies is always the empty string.
   POLICY_DOMAIN_CHROME,
@@ skipping 21 matching lines @@
   bool operator!=(const PolicyNamespace& other) const;
 
   PolicyDomain domain;
   std::string component_id;
 };
 
 typedef std::vector<PolicyNamespace> PolicyNamespaceList;
 
 }  // namespace policy
 
+// Define a custom std::hash for PolicyNamespace so that it can be used as
+// a key in hash_maps, and in particular in ScopedPtrHashMaps (which use the
+// default std::hash).
+namespace BASE_HASH_NAMESPACE {
+
+template <>
+struct hash<policy::PolicyNamespace> {
+  std::size_t operator()(const policy::PolicyNamespace& ns) const {
+    return hash<std::string>()(ns.component_id) ^ (1 << ns.domain);
+  }
+};
+
+}  // namespace BASE_HASH_NAMESPACE
+
 #endif  // COMPONENTS_POLICY_CORE_COMMON_POLICY_NAMESPACE_H_