Make unknown extension subpermissions warnings instead of errors.

extensions/common/permissions/api_permission.cc

Index: extensions/common/permissions/api_permission.cc
diff --git a/extensions/common/permissions/api_permission.cc b/extensions/common/permissions/api_permission.cc
index 95728fa1cf303cb8a4a112661dc86bd0653482b4..b757cf249d205c8741807653b4e71c415ef3f915 100644
--- a/extensions/common/permissions/api_permission.cc
+++ b/extensions/common/permissions/api_permission.cc
@@ -47,8 +47,10 @@ class SimpleAPIPermission : public APIPermission {
     return true;
   }
 
-  virtual bool FromValue(const base::Value* value,
-                         std::string* /*error*/) OVERRIDE {
+  virtual bool FromValue(
+      const base::Value* value,
+      std::string* /*error*/,
+      std::vector<std::string>* /*unhandled_permissions*/) OVERRIDE {
     return (value == NULL);
   }