Use STLClearObject in URLFetcherCore

net/url_request/url_fetcher_core.cc

Index: net/url_request/url_fetcher_core.cc
diff --git a/net/url_request/url_fetcher_core.cc b/net/url_request/url_fetcher_core.cc
index ff5e5d4da34fcb68077bbe83363649de23844d3e..9958e2f60a9629708fb587a94fa3964d246ddc6b 100644
--- a/net/url_request/url_fetcher_core.cc
+++ b/net/url_request/url_fetcher_core.cc
@@ -197,7 +197,7 @@ void URLFetcherCore::SetChunkedUpload(const std::string& content_type) {
   DCHECK(!content_type.empty());
 
   upload_content_type_ = content_type;
-  upload_content_.clear();
+  base::STLClearObject(&upload_content_);
   is_chunked_upload_ = true;
 }