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BUG=webrtc:4183
R=andrew@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/36759004

Patch from Richard Coles <torne@chromium.org>.

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#8658}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: a3823e29a2b0b8e82946dcefa60b4187660965f4

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