Change default name of crostini backup to chromeos-linux-yyyy-mm-dd.tar.gz

Bug: 945959
Change-Id: Ia611b7edcf3c123b0885e8ea4a69d72e035acfd1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1539629
Auto-Submit: Joel Hockey <joelhockey@chromium.org>
Commit-Queue: Nicholas Verne <nverne@chromium.org>
Reviewed-by: Nicholas Verne <nverne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#644574}

chrome/browser/chromeos/crostini/crostini_export_import.cc

@@ -109,10 +109,11 @@ void CrostiniExportImport::OpenFileDialog(ExportImportType type,
       title = IDS_SETTINGS_CROSTINI_EXPORT;
       base::Time::Exploded exploded;
       base::Time::Now().LocalExplode(&exploded);
-      default_path = pref_service->GetFilePath(prefs::kDownloadDefaultDirectory)
-                         .Append(base::StringPrintf(
-                             "crostini-%04d-%02d-%02d.tar.gz", exploded.year,
-                             exploded.month, exploded.day_of_month));
+      default_path =
+          pref_service->GetFilePath(prefs::kDownloadDefaultDirectory)
+              .Append(base::StringPrintf("chromeos-linux-%04d-%02d-%02d.tar.gz",
+                                         exploded.year, exploded.month,
+                                         exploded.day_of_month));
       break;
     case ExportImportType::IMPORT:
       file_selector_mode = ui::SelectFileDialog::SELECT_OPEN_FILE,