Put ViEFrameProviderBase::DeliverFrame back in the critical section in ViECapturer::DeliverI420Frame
Put ViEFrameProviderBase::DeliverFrame back in the critical section in ViECapturer::DeliverI420Frame

The CL that moved it out of the critical section is here: https://webrtc-codereview.appspot.com/43669004/

BUG=1128
R=tommi@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/45679005

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#8724}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 6107ba12f9d2364aced90046675ba6cceea19966

sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc