Fix dangling pointer in screenshare_loopback
Fix dangling pointer in screenshare_loopback

BUG=
R=pbos@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/52369004

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#9098}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 9d657cfd664122541086e5ab7ca19b25f1c4b90e

krieger-od/webrtc,sippet/webrtc,aleonliao/webrtc-trunk,jchavanton/webrtc,krieger-od/webrtc,krieger-od/webrtc,aleonliao/webrtc-trunk,Alkalyne/webrtctrunk,aleonliao/webrtc-trunk,jchavanton/webrtc,jchavanton/webrtc,aleonliao/webrtc-trunk,jchavanton/webrtc,aleonliao/webrtc-trunk,Alkalyne/webrtctrunk,aleonliao/webrtc-trunk,jchavanton/webrtc,sippet/webrtc,sippet/webrtc,Alkalyne/webrtctrunk,sippet/webrtc,krieger-od/webrtc,krieger-od/webrtc,Alkalyne/webrtctrunk,jchavanton/webrtc,Alkalyne/webrtctrunk,krieger-od/webrtc,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,sippet/webrtc,sippet/webrtc,jchavanton/webrtc