Merge third_party/webrtc from https://chromium.googlesource.com/external/webrtc/trunk/webrtc.git at a288b8cbb568cbf1735e6d5d0012524f4f8e5f74

This commit was generated by merge_from_chromium.py.

Change-Id: I7111bd9dfbd0189653b56a787e5d5583b1f479d7