Fix a time control bug, that the VCMReceiver::FrameForDecoding may over sleep.
Fix a time control bug, that the VCMReceiver::FrameForDecoding may over sleep.

Remark: a unit test to verify VCMReiceiver::FrameForDecoding will be in a separate CL.

BUG=4726
R=stefan@webrtc.org, wtc@chromium.org

Review URL: https://webrtc-codereview.appspot.com/53619004

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#9362}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: b4c5eaa0d6def89548ff30853096e9b13dde07f2

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