Ignore unknown attributes when parsing JSON schemas.

components/policy/core/common/schema.cc

Index: components/policy/core/common/schema.cc
diff --git a/components/policy/core/common/schema.cc b/components/policy/core/common/schema.cc
index 0129094c75a0da6773318f81e40b3dfca581177c..bdeeaba624fc3add826060d897ad1308096fd2c8 100644
--- a/components/policy/core/common/schema.cc
+++ b/components/policy/core/common/schema.cc
@@ -500,9 +500,10 @@ bool Schema::Validate(const base::Value& value) const {
 
 // static
 Schema Schema::Parse(const std::string& content, std::string* error) {
-  // Validate as a generic JSON schema.
+  // Validate as a generic JSON schema, and ignore unknown attributes; they
+  // may become used in a future version of the schema format.
   scoped_ptr<base::DictionaryValue> dict =
-      JSONSchemaValidator::IsValidSchema(content, error);
+      JSONSchemaValidator::IsValidSchema(content, false, error);
   if (!dict)
     return Schema();