Revert of Flag covering Rollback removed.

chrome/browser/ui/webui/chromeos/login/reset_screen_handler.cc

Index: chrome/browser/ui/webui/chromeos/login/reset_screen_handler.cc
diff --git a/chrome/browser/ui/webui/chromeos/login/reset_screen_handler.cc b/chrome/browser/ui/webui/chromeos/login/reset_screen_handler.cc
index 62aa6e0fd0381521dfe6413b141b091b449129a6..da3063a1a34a435b87a48bf89005232e31881e24 100644
--- a/chrome/browser/ui/webui/chromeos/login/reset_screen_handler.cc
+++ b/chrome/browser/ui/webui/chromeos/login/reset_screen_handler.cc
@@ -6,7 +6,13 @@
 
 #include <string>
 
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/callback.h"
 #include "base/command_line.h"
+#include "base/file_util.h"
+#include "base/files/file_path.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/metrics/histogram.h"
 #include "base/prefs/pref_registry_simple.h"
 #include "base/prefs/pref_service.h"
@@ -36,6 +42,13 @@
 
 const int kErrorUIStateRollback = 7;
 
+static const char kRollbackFlagFile[] = "/tmp/.enable_rollback_ui";
+
+void CheckRollbackFlagFileExists(bool *file_exists) {
+  DCHECK(content::BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
+  *file_exists = base::PathExists(base::FilePath(kRollbackFlagFile));
+}
+
 }  // namespace
 
 namespace chromeos {
@@ -110,8 +123,28 @@
   if (!restart_required_)  // First exec after boot.
     reboot_was_requested_ = prefs->GetBoolean(prefs::kFactoryResetRequested);
 
-  if (CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kDisableRollbackOption)) {
+  // Check Rollback flag-file.
+  scoped_ptr<bool> file_exists(new bool(false));
+  base::Closure checkfile_closure = base::Bind(
+      &CheckRollbackFlagFileExists,
+      base::Unretained(file_exists.get()));
+  base::Closure on_check_done = base::Bind(
+      &ResetScreenHandler::OnRollbackFlagFileCheckDone,
+      weak_ptr_factory_.GetWeakPtr(),
+      base::Passed(file_exists.Pass()));
+  if (!content::BrowserThread::PostBlockingPoolTaskAndReply(
+          FROM_HERE,
+          checkfile_closure,
+          on_check_done)) {
+    LOG(WARNING) << "Failed to check flag file for Rollback reset option";
+    on_check_done.Run();
+  }
+}
+
+void ResetScreenHandler::OnRollbackFlagFileCheckDone(
+    scoped_ptr<bool> file_exists) {
+  if (!(*file_exists) && !CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnableRollbackOption)) {
     rollback_available_ = false;
     ShowWithParams();
   } else if (!restart_required_ && reboot_was_requested_) {