ClientSocketPool:  Add argument to CancelRequest to cancel ConnectJobs

When requests end up using H2 connection pooling (Or even just using
an H2 connection established for another request), any in-progress
ConnectJobs won't be needed, so we should be able to abort them.

The new argument won't help us do anything about backup ConnectJobs,
created if the original request was taking too long, or multiple
ConnectJobs created for other reasons (Start 2 requests to a server,
cancel 1 of them for other reasons, and the other establishes an
H2 connection, and the other ConnectJob may still complete
successfully, and just be left idle in the socket pool).

Bug: 912727
Change-Id: I0428534a542b863866639412f82a3023df3d7066
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1582324
Commit-Queue: Matt Menke <mmenke@chromium.org>
Reviewed-by: David Benjamin <davidben@chromium.org>
Cr-Commit-Position: refs/heads/master@{#654186}
13 files changed