Fixed error for missing explicit class initialization error on iOS buildbots
Fixed error for missing explicit class initialization error on iOS buildbots

TBR=henrik.lundin@webrtc.org

BUG=webrtc:6018

Review-Url: https://codereview.webrtc.org/2799813002
Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#17549}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 5ac18af71b0805678fcf78b32b3c7d6aa62bea71

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