Enable WebSockets over HTTP/2.

Change HttpStreamFactoryImpl::Job to allow secure WebSocket requests to
use an existing HTTP/2 connection if the server has already indicated
support.  If no such connection exists, a new non-HTTP/2 connection is
created for the WebSocket request just like before.

Bug: 801564
Change-Id: I72541fcb8c88906699bf85ff305f2b2d590095ca
Reviewed-on: https://chromium-review.googlesource.com/905344
Commit-Queue: Bence Béky <bnc@chromium.org>
Reviewed-by: Adam Rice <ricea@chromium.org>
Cr-Commit-Position: refs/heads/master@{#538584}
3 files changed