Pass the previous and the current PolicyMap to Observers of the PolicyService.

chrome/browser/policy/policy_service_impl.cc

Index: chrome/browser/policy/policy_service_impl.cc
diff --git a/chrome/browser/policy/policy_service_impl.cc b/chrome/browser/policy/policy_service_impl.cc
index 5083a0cf490d2961c10927126d347943d1d902aa..14710c4aa18ac347598b8e67383c6a86dac7f38e 100644
--- a/chrome/browser/policy/policy_service_impl.cc
+++ b/chrome/browser/policy/policy_service_impl.cc
@@ -125,18 +125,23 @@ void PolicyServiceImpl::MaybeCleanup(const PolicyNamespace& ns) {
 void PolicyServiceImpl::MergeAndTriggerUpdates() {
   // TODO(joaodasilva): do this for each namespace once the providers also
   // provide policy for more namespaces.
-  PolicyMap new_policies;
+  PolicyMap policies;
   for (ProviderList::iterator it = providers_.begin();
        it != providers_.end(); ++it) {
-    new_policies.MergeFrom((*it)->policies);
+    policies.MergeFrom((*it)->policies);
   }
 
   Entry* entry = GetOrCreate(std::make_pair(POLICY_DOMAIN_CHROME, ""));
-  if (!new_policies.Equals(entry->policies)) {
-    entry->policies.Swap(&new_policies);
-    FOR_EACH_OBSERVER(PolicyService::Observer,
-                      entry->observers,
-                      OnPolicyUpdated(POLICY_DOMAIN_CHROME, ""));
+  if (!policies.Equals(entry->policies)) {
+    // Swap first, so that observers that call GetPolicies() see the current
+    // values.
+    entry->policies.Swap(&policies);
+    // |policies| now contains the previous values, and |entry->policies|
+    // contains the current values.

[Mattias Nissler (ping if slow), 2012/04/23 14:20:44]

I think this comment is redundant and can be removed (it just explains the
behavior of the Swap one line before, which does exactly what it's expected to
do).

[Joao da Silva, 2012/04/23 14:53:19]

Done.

+    FOR_EACH_OBSERVER(
+        PolicyService::Observer,
+        entry->observers,
+        OnPolicyUpdated(POLICY_DOMAIN_CHROME, "", policies, entry->policies));
   }
 
   // Check if all providers became initialized just now, if they weren't before.