Move pushed url collision detection to UnclaimedPushedStreamContainer.

Move pushed url collision detection from
SpdySession::TryCreatePushStream() to
UnclaimedPushedStreamContainer::insert().  This is a refactoring with
little functional change (request method is now checked before URL
collision, not after).

My plan is to only allow at most one pushed stream per URL across all
SpdySessions, and this CL is in preparation for that change.

Bug: 554220
Change-Id: Ib4db703c6a7b267aceeee0e77ea694d048017cc8
Reviewed-on: https://chromium-review.googlesource.com/701839
Reviewed-by: Helen Li <xunjieli@chromium.org>
Commit-Queue: Bence Béky <bnc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#507090}
2 files changed