Fixes and improvements to cloud policy for extensions.

components/policy/core/common/schema_registry.cc

Index: components/policy/core/common/schema_registry.cc
diff --git a/components/policy/core/common/schema_registry.cc b/components/policy/core/common/schema_registry.cc
index 16f71e5318a6345c5afd03fa52ff912a23508b20..ff9557956f3fcde42a78097caccd60f814d825bc 100644
--- a/components/policy/core/common/schema_registry.cc
+++ b/components/policy/core/common/schema_registry.cc
@@ -29,6 +29,9 @@ void SchemaRegistry::RegisterComponent(const PolicyNamespace& ns,
 
 void SchemaRegistry::RegisterComponents(PolicyDomain domain,
                                         const ComponentMap& components) {
+  // Don't issue notifications if nothing is being registered.
+  if (components.empty())
+    return;
   // Assume that a schema was updated if the namespace was already registered
   // before.
   DomainMap map(schema_map_->GetDomains());