Use std::abs instead of C-style abs.
Use std::abs instead of C-style abs.

BUG=webrtc:6486

Review-Url: https://codereview.webrtc.org/2396823002
Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#14536}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: a84aa57799fc4c7c832ba2e3614195b5231baa24

Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk