[DIPS] Add repeating timer to the DIPS profile-keyed service.

This CL just adds the PersistentRepeatingTimer and required prefs. The
period of the timer is temporarily set to 24hrs, but will be updated in
future CLs. Future CLs will also implement the behavior that we want to
occur when the timer reaches its period.

Bug: 1375302
Change-Id: I60d72ba4412aa27d12ee4080ab8ea0945a690d5b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4006254
Reviewed-by: Ben Kelly <[email protected]>
Commit-Queue: Kirubel Aklilu <[email protected]>
Reviewed-by: Lei Zhang <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1069865}
diff --git a/chrome/browser/prefs/browser_prefs.cc b/chrome/browser/prefs/browser_prefs.cc
index 1c251b5..8792315 100644
--- a/chrome/browser/prefs/browser_prefs.cc
+++ b/chrome/browser/prefs/browser_prefs.cc
@@ -1642,6 +1642,8 @@
   registry->RegisterBooleanPref(prefs::kVirtualKeyboardResizesLayoutByDefault,
                                 false);
 #endif
+
+  registry->RegisterTimePref(prefs::kDIPSTimerLastUpdate, base::Time());
 }
 
 void RegisterUserProfilePrefs(user_prefs::PrefRegistrySyncable* registry) {