[aw] Fix null pointer dereference in aw_url_request_context_getter

Fix trying to access the proxy_config_service that was moved to the
url_request_context in InitializeURLRequestContext

Bug: 851995
Change-Id: Icc31c661ff4bd0e6b92d899a9d427ed75db0a295
Reviewed-on: https://chromium-review.googlesource.com/1234154
Reviewed-by: Matt Menke <mmenke@chromium.org>
Reviewed-by: Tobias Sargeant <tobiasjs@chromium.org>
Commit-Queue: Laís Minchillo <laisminchillo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593140}
2 files changed