QualityScaler reset bugfix
QualityScaler reset bugfix

BUG=webrtc:6563
TBR=sprang@webrtc.org

Review-Url: https://codereview.webrtc.org/2434803002
Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#14688}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 55928fef1e1579debf442b17b39007e0525e03a4

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