GitLab

This is accomplished by avoiding holding Cronet_UrlRequestImpl::lock_
while issuing callbacks. Holding the lock is only necessary while
modifying state that should be processed in an atomic fashion.
The Cronet_UrlRequestImpl will not be deleted until after final
callbacks have been run so there is no chance of a use-after-free.

Bug: 869402
Cq-Include-Trybots: master.tryserver.chromium.android:android_cronet_tester;luci.chromium.try:ios-simulator-cronet
Change-Id: Ie851b57296c394e6f098022a7930d65f62f7b0c6
Reviewed-on: https://chromium-review.googlesource.com/1183625Reviewed-by: Misha Efimov <mef@chromium.org>
Cr-Commit-Position: refs/heads/master@{#587203}