[Sync] Migrate SyncInternalsMessageHandler off CallJavascriptFunctionUnsafe.

components/browser_sync/profile_sync_service.cc

Index: components/browser_sync/profile_sync_service.cc
diff --git a/components/browser_sync/profile_sync_service.cc b/components/browser_sync/profile_sync_service.cc
index df12c63fe92a5f8feed337c1d4c2c15162942f71..cf5f2af870f249567be498da4bd053ccbd2a2791 100644
--- a/components/browser_sync/profile_sync_service.cc
+++ b/components/browser_sync/profile_sync_service.cc
@@ -2194,13 +2194,6 @@ bool ProfileSyncService::IsSyncRequested() const {
   return sync_prefs_.IsSyncRequested() || sync_prefs_.IsLocalSyncEnabled();
 }
 
-SigninManagerBase* ProfileSyncService::signin() const {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  if (!signin_)
-    return nullptr;
-  return signin_->GetOriginal();
-}
-
 void ProfileSyncService::RequestStart() {
   DCHECK(thread_checker_.CalledOnValidThread());
   if (!IsSyncAllowed()) {