[Extensions] Isolate ExtensionFunction results_ and error_

extensions/browser/api/web_request/web_request_api.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "extensions/browser/api/web_request/web_request_api.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <memory>
@@ skipping 1961 matching lines @@
 void ClearCacheQuotaHeuristic::OnPageLoad(Bucket* bucket) {
   callback_registered_ = false;
   bucket->DeductToken();
 }
 
 ExtensionFunction::ResponseAction
 WebRequestInternalAddEventListenerFunction::Run() {
   // Argument 0 is the callback, which we don't use here.
   ExtensionWebRequestEventRouter::RequestFilter filter;
   base::DictionaryValue* value = NULL;
-  error_.clear();

[lazyboy, 2016/09/30 01:16:05]

I see this was added in https://codereview.chromium.org/6880219, could there be
any side effect removing this?

[Devlin, 2016/09/30 18:29:09]

There shouldn't be.  Run() should never be called if there's an existing error.

   EXTENSION_FUNCTION_VALIDATE(args_->GetDictionary(1, &value));
   // Failure + an empty error string means a fatal error.
-  EXTENSION_FUNCTION_VALIDATE(filter.InitFromValue(*value, &error_) ||
-                              !error_.empty());
-  if (!error_.empty())
-    return RespondNow(Error(error_));
+  std::string error;
+  EXTENSION_FUNCTION_VALIDATE(filter.InitFromValue(*value, &error) ||
+                              !error.empty());
+  if (!error.empty())
+    return RespondNow(Error(error));
 
   int extra_info_spec = 0;
   if (HasOptionalArgument(2)) {
     base::ListValue* value = NULL;
     EXTENSION_FUNCTION_VALIDATE(args_->GetList(2, &value));
     EXTENSION_FUNCTION_VALIDATE(
         ExtraInfoSpec::InitFromValue(*value, &extra_info_spec));
   }
 
   std::string event_name;
@@ skipping 263 matching lines @@
   // Since EventListeners are segmented by browser_context, check that
   // last, as it is exceedingly unlikely to be different.
   return extension_id == that.extension_id &&
          sub_event_name == that.sub_event_name &&
          web_view_instance_id == that.web_view_instance_id &&
          embedder_process_id == that.embedder_process_id &&
          browser_context == that.browser_context;
 }
 
 }  // namespace extensions