Fix potential SEGV issue.

chrome/browser/ui/webui/feedback_ui.cc

Index: chrome/browser/ui/webui/feedback_ui.cc
diff --git a/chrome/browser/ui/webui/feedback_ui.cc b/chrome/browser/ui/webui/feedback_ui.cc
index 8579ea9c554df4b624d08d84b33b463bd7ebf1fc..2cbbad82a933c068e5d8fc9c146e0c806885af8a 100644
--- a/chrome/browser/ui/webui/feedback_ui.cc
+++ b/chrome/browser/ui/webui/feedback_ui.cc
@@ -62,7 +62,6 @@
 #include "base/file_util.h"
 #include "base/path_service.h"
 #include "chrome/browser/chromeos/drive/drive.pb.h"
-#include "chrome/browser/chromeos/drive/drive_integration_service.h"
 #include "chrome/browser/chromeos/drive/file_system_interface.h"
 #include "chrome/browser/chromeos/drive/file_system_util.h"
 #include "chrome/browser/chromeos/login/user_manager.h"
@@ -582,8 +581,12 @@ void FeedbackHandler::GetMostRecentScreenshotsDrive(
     const base::FilePath& filepath, std::vector<std::string>* saved_screenshots,
     size_t max_saved, base::Closure callback) {
   drive::FileSystemInterface* file_system =
-      drive::DriveIntegrationServiceFactory::GetForProfile(
-          Profile::FromWebUI(web_ui()))->file_system();
+      drive::util::GetFileSystemByProfile(Profile::FromWebUI(web_ui()));
+  if (!file_system) {
+    callback.Run();
+    return;
+  }
+
   file_system->ReadDirectoryByPath(
       drive::util::ExtractDrivePath(filepath),
       base::Bind(&ReadDirectoryCallback, max_saved, saved_screenshots,