Added support for multiple parameters to Extension API callbacks.

chrome/browser/extensions/api/downloads/downloads_api.cc

Index: chrome/browser/extensions/api/downloads/downloads_api.cc
diff --git a/chrome/browser/extensions/api/downloads/downloads_api.cc b/chrome/browser/extensions/api/downloads/downloads_api.cc
index 49e8f77f553440ca3f2a4d7be78c38cf922222d9..dc89d1322895fb24272a321d2ff391ab80562138 100644
--- a/chrome/browser/extensions/api/downloads/downloads_api.cc
+++ b/chrome/browser/extensions/api/downloads/downloads_api.cc
@@ -544,7 +544,7 @@ void DownloadsDownloadFunction::OnStarted(DownloadId dl_id, net::Error error) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   VLOG(1) << __FUNCTION__ << " " << dl_id << " " << error;
   if (dl_id.local() >= 0) {
-    result_.reset(base::Value::CreateIntegerValue(dl_id.local()));
+    SetSingleResult(base::Value::CreateIntegerValue(dl_id.local()));
   } else {
     error_ = net::ErrorToString(error);
   }
@@ -677,7 +677,7 @@ bool DownloadsSearchFunction::RunInternal() {
     scoped_ptr<base::DictionaryValue> item(DownloadItemToJSON(*it));
     json_results->Append(item.release());
   }
-  result_.reset(json_results);
+  SetSingleResult(json_results);
   return true;
 }
 
@@ -911,7 +911,7 @@ void DownloadsGetFileIconFunction::OnIconURLExtracted(const std::string& url) {
   if (url.empty())
     error_ = download_extension_errors::kIconNotFoundError;
   else
-    result_.reset(base::Value::CreateStringValue(url));
+    SetSingleResult(base::Value::CreateStringValue(url));
   SendResponse(error_.empty());
 }