Use container::back() and container::pop_back().

storage/browser/fileapi/file_system_url_request_job_factory.cc

Index: storage/browser/fileapi/file_system_url_request_job_factory.cc
diff --git a/storage/browser/fileapi/file_system_url_request_job_factory.cc b/storage/browser/fileapi/file_system_url_request_job_factory.cc
index 90dd81fad82d9a7b9c99b392304df6eb31ad2b97..f2481b5a896fcd79cc097d295b81ed560914383a 100644
--- a/storage/browser/fileapi/file_system_url_request_job_factory.cc
+++ b/storage/browser/fileapi/file_system_url_request_job_factory.cc
@@ -52,7 +52,7 @@ net::URLRequestJob* FileSystemProtocolHandler::MaybeCreateJob(
   // If the path ends with a /, we know it's a directory. If the path refers
   // to a directory and gets dispatched to FileSystemURLRequestJob, that class
   // redirects back here, by adding a / to the URL.
-  if (!path.empty() && path[path.size() - 1] == '/') {
+  if (!path.empty() && path.back() == '/') {
     return new FileSystemDirURLRequestJob(
         request, network_delegate, storage_domain_, file_system_context_);
   }