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.org TBR=henrikg@webrtc.org Review URL: https://codereview.webrtc.org/1473713004 . Cr-Commit-Position: refs/heads/master@{#10793}