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

components/policy/core/common/cloud/cloud_policy_client.h

Index: components/policy/core/common/cloud/cloud_policy_client.h
diff --git a/components/policy/core/common/cloud/cloud_policy_client.h b/components/policy/core/common/cloud/cloud_policy_client.h
index bcf43530890981f62d1a4ea6778527451b772dac..3a8b68eb9f45ace9877033aa343b11dde3ba932c 100644
--- a/components/policy/core/common/cloud/cloud_policy_client.h
+++ b/components/policy/core/common/cloud/cloud_policy_client.h
@@ -38,6 +38,9 @@ class DeviceManagementService;
 // installed in the cloud policy cache.
 class POLICY_EXPORT CloudPolicyClient {
  public:
+  // A set of PolicyNamespaceKeys to fetch.
+  typedef std::set<PolicyNamespaceKey> NamespaceSet;
+
   // Maps a PolicyNamespaceKey to its corresponding PolicyFetchResponse.
   typedef std::map<PolicyNamespaceKey,
                    enterprise_management::PolicyFetchResponse*> ResponseMap;
@@ -196,6 +199,14 @@ class POLICY_EXPORT CloudPolicyClient {
     return responses_;
   }
 
+  // Returns a set with the policy namespaces that were included in the fetch
+  // request that produced the current |responses()|. This can be used to
+  // determine if a namespace is missing because it wasn't requested or because
+  // the server didn't include a response.

[Mattias Nissler (ping if slow), 2014/11/26 13:44:14]

Hm, this moves the responsibility to do the diffing on calling code. Can't we
just store NULL entries in the map returned by responses()?

Following up on the offline conversation: How about we pass the PolicyNamespace
set for extensions to the client and have the client reduce it to just a single
PolicyNamespace(EXTENSIONS, "") for the request? Then, we'd have all requested
namespaces present in ResponseMap, and a NULL indicates that the server didn't
provide a response.

After another discussion, there's the problem here that we'd all the namespaces
to be added before making the first fetch, which causes initialization
nightmares. Needs further thought.

+  const NamespaceSet& namespaces_requested() const {
+    return namespaces_requested_;
+  }
+
   // Returns the policy response for |policy_ns_key|, if found in |responses()|;
   // otherwise returns NULL.
   const enterprise_management::PolicyFetchResponse* GetPolicyFor(
@@ -219,9 +230,6 @@ class POLICY_EXPORT CloudPolicyClient {
   scoped_refptr<net::URLRequestContextGetter> GetRequestContext();
 
  protected:
-  // A set of PolicyNamespaceKeys to fetch.
-  typedef std::set<PolicyNamespaceKey> NamespaceSet;
-
   // Callback for retries of registration requests.
   void OnRetryRegister(DeviceManagementRequestJob* job);
 
@@ -233,6 +241,7 @@ class POLICY_EXPORT CloudPolicyClient {
 
   // Callback for policy fetch requests.
   void OnPolicyFetchCompleted(
+      const NamespaceSet& namespaces_requested,
       DeviceManagementStatus status,
       int net_error,
       const enterprise_management::DeviceManagementResponse& response);
@@ -297,6 +306,9 @@ class POLICY_EXPORT CloudPolicyClient {
   ResponseMap responses_;
   DeviceManagementStatus status_;
 
+  // The namespaces that were requested in the last successful policy fetch.
+  NamespaceSet namespaces_requested_;
+
   ObserverList<Observer, true> observers_;
   scoped_refptr<net::URLRequestContextGetter> request_context_;