AviRecorder is missing a critical section.

BUG=2885
TEST=AUTOTEST
R=perkj@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/9039004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@5600 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/utility/source/file_recorder_impl.cc

@@ -715,6 +715,8 @@ int32_t AviRecorder::WriteEncodedAudioData(
     uint16_t millisecondsOfData,
     const TickTime* playoutTS)
 {
+    CriticalSectionScoped lock(_critSec);
+
     if (!IsRecording())
     {
         return -1;