Hint at prefs/README.md from browser_prefs.cc

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Change-Id: I4431bfadfc5bc1c377297041018a7bede3e34379
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2827113
Commit-Queue: Gabriel Charette <[email protected]>
Commit-Queue: Dominic Battré <[email protected]>
Auto-Submit: Gabriel Charette <[email protected]>
Reviewed-by: Dominic Battré <[email protected]>
Cr-Commit-Position: refs/heads/master@{#872908}
diff --git a/chrome/browser/prefs/browser_prefs.cc b/chrome/browser/prefs/browser_prefs.cc
index 6df5cd9..627eadf1 100644
--- a/chrome/browser/prefs/browser_prefs.cc
+++ b/chrome/browser/prefs/browser_prefs.cc
@@ -1207,6 +1207,7 @@
 #endif
 
 // This method should be periodically pruned of year+ old migrations.
+// See chrome/browser/prefs/README.md for details.
 void MigrateObsoleteLocalStatePrefs(PrefService* local_state) {
   // BEGIN_MIGRATE_OBSOLETE_LOCAL_STATE_PREFS
   // Please don't delete the preceding line. It is used by PRESUBMIT.py.
@@ -1254,6 +1255,7 @@
 }
 
 // This method should be periodically pruned of year+ old migrations.
+// See chrome/browser/prefs/README.md for details.
 void MigrateObsoleteProfilePrefs(Profile* profile) {
   // BEGIN_MIGRATE_OBSOLETE_PROFILE_PREFS
   // Please don't delete the preceding line. It is used by PRESUBMIT.py.