Fixes data race in WebRTCAudioDeviceTest.Construct reported by ThreadSanitizer

BUG=159112

Review URL: https://webrtc-codereview.appspot.com/1201007

git-svn-id: http://webrtc.googlecode.com/svn/trunk@3750 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/modules/utility/source/process_thread_impl.cc b/webrtc/modules/utility/source/process_thread_impl.cc
index 9028c44..bdbd5ca 100644
--- a/webrtc/modules/utility/source/process_thread_impl.cc
+++ b/webrtc/modules/utility/source/process_thread_impl.cc
@@ -164,6 +164,7 @@
         {
             return true;
         }
+        CriticalSectionScoped lock(_critSectModules);
         if(!_thread)
         {
             return false;