Re-landing perf improvement for libjingle logging after reverting the general change.
This contains only a part of r8635 that I just reverted to unblock the roll.

TBR=perkj@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/42259004

Cr-Original-Commit-Position: refs/heads/master@{#8643}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: f696e49c9a19817dfbb6c766a6d98ac2336b14e8
1 file changed