Removes log disabling under Chromium which doesn't compile due to
missing LS_INFO in the override log implementation.
Also removes dependency on webrtc/test/BUILD.gn which doesn't build in
Chromium (due to third_party/gflags not being present). Instead the
no-op implementation of field_trials in system_wrappers is used.
BUG=chromium:561667, webrtc:4771
R=kjellander@webrtc.orgTBR=henrikg@webrtc.org
Review URL: https://codereview.webrtc.org/1473713004 .
Cr-Commit-Position: refs/heads/master@{#10793}