Refactored users of PolicySchema to use the new policy::Schema class.

components/policy/core/common/schema.h

Index: components/policy/core/common/schema.h
diff --git a/components/policy/core/common/schema.h b/components/policy/core/common/schema.h
index a81b7adae30fe8e78c34b7c8a2b86a102956f34e..7a734bf02110cda5ad1c967adbb4d7f9606b6c6d 100644
--- a/components/policy/core/common/schema.h
+++ b/components/policy/core/common/schema.h
@@ -30,7 +30,14 @@ struct POLICY_EXPORT PropertiesNode;
 // Use the SchemaOwner class to parse a schema and get Schema objects.
 class POLICY_EXPORT Schema {
  public:
+  // Builds an empty, invalid schema.
+  Schema();
+
+  // Builds a schema pointing to the inner structure of |schema|. If |schema|
+  // is NULL then this Schema instance will be invalid.
+  // Does not take ownership of |schema|.
   explicit Schema(const internal::SchemaNode* schema);
+
   Schema(const Schema& schema);
 
   Schema& operator=(const Schema& schema);