Eliminates a dependency on system_wrappers and the FileWrapper class. Bug: None Change-Id: I2cbbf4d6c3bf50e9b3b0b6d140da6d5d7e54167e Reviewed-on: https://webrtc-review.googlesource.com/29821 Commit-Queue: Niels Moller <nisse@webrtc.org> Reviewed-by: Elad Alon <eladalon@webrtc.org> Reviewed-by: Björn Terelius <terelius@webrtc.org> Cr-Commit-Position: refs/heads/master@{#21208}