GitLab

mplement SharedModelTypeProcessor::GetAllNodes for USS, so
"Sync Node Browser" tab in chrome://sync-internals/ will show
USS data.
BTW, modelTypeWorker already ignore the root folder from
server.

BUG=645303

Review-Url: https://codereview.chromium.org/2319973003
Cr-Commit-Position: refs/heads/master@{#418735}