When authenticated user visits root url like
https://gerrit-review.googlesource.com/ frontend will redirect to
dashboard/self without informing backend.
We need to preload for both root url and dashboard/self. From data
it looks root path is 10x more visited than dashboard/self, although
many visits to root path could be made by guests.
+ preload dashboard queries only when the user is logged in.
Change-Id: I73158d98fe8d6d77dcbbfbb70ebc96609d1854b8
d291cbf362