[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-Original-Commit-Position: refs/heads/master@{#593140}(cherry picked from commit 08260e4c1445f7d2986843299671ed11787b8c7b)
Reviewed-on: https://chromium-review.googlesource.com/1243144
Cr-Commit-Position: refs/branch-heads/3538@{#649}
Cr-Branched-From: 79f7c91a2b2a2932cd447fa6f865cb6662fa8fa6-refs/heads/master@{#587811}
2 files changed