Adds cache lock timeout handling after finishing headers phase.

Since now there is parallel validation of requests but the cache lock
still applies when the writer transaction is reading the response body
we need to have a lock timeout handling when a transaction is waiting
in the done_headers_queue as well.

This Cl also removes the unused RestartInfo structure definition.

BUG=735998

Review-Url: https://codereview.chromium.org/2953983003
Cr-Commit-Position: refs/heads/master@{#482148}
7 files changed