ServiceWorkerOnUI: Add Chrome flag.

This will make it easy to test the feature on Android without needing
a command-line flag.

Bug: 824858
Change-Id: I26736f1c2edbad635d9030f9d35939ace6daa799
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1833026
Commit-Queue: Matt Falkenhagen <[email protected]>
Reviewed-by: Hiroki Nakagawa <[email protected]>
Cr-Commit-Position: refs/heads/master@{#701564}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index 7a8b0d1..0be88b6 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -1067,6 +1067,9 @@
 extern const char kServiceWorkerLongRunningMessageName[];
 extern const char kServiceWorkerLongRunningMessageDescription[];
 
+extern const char kServiceWorkerOnUIName[];
+extern const char kServiceWorkerOnUIDescription[];
+
 extern const char kSessionRestorePrioritizesBackgroundUseCasesName[];
 extern const char kSessionRestorePrioritizesBackgroundUseCasesDescription[];