Avoid unsafe usage of CancelIo() within Windows SyncSocket.

media/audio/audio_device_thread.cc

Index: media/audio/audio_device_thread.cc
diff --git a/media/audio/audio_device_thread.cc b/media/audio/audio_device_thread.cc
index b8ae3f903196320800c25bf176bae17ec382c21e..172033f46cb63a33fb9eaf79226a209804f0ba32 100644
--- a/media/audio/audio_device_thread.cc
+++ b/media/audio/audio_device_thread.cc
@@ -166,10 +166,8 @@ void AudioDeviceThread::Thread::Run() {
   while (true) {
     int pending_data = 0;
     size_t bytes_read = socket_.Receive(&pending_data, sizeof(pending_data));
-    if (bytes_read != sizeof(pending_data)) {
-      DCHECK_EQ(bytes_read, 0U);
+    if (bytes_read != sizeof(pending_data))
       break;
-    }
 
     {
       base::AutoLock auto_lock(callback_lock_);