Uncomment commented-out sequence-checks in call.cc

Two of the three commented-out checks should have been fixed by https://codereview.webrtc.org/2998923002/. The last will be fixed in a separate CL.

BUG=webrtc:8116

Review-Url: https://codereview.webrtc.org/2999253002
Cr-Original-Commit-Position: refs/heads/master@{#19511}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: d1dd2f79e5f290ef0f21f5c050aa0111732a0f71
1 file changed