V4L2VDA: fix starting the device poll thread twice.

media/gpu/v4l2_video_decode_accelerator.cc

Index: media/gpu/v4l2_video_decode_accelerator.cc
diff --git a/media/gpu/v4l2_video_decode_accelerator.cc b/media/gpu/v4l2_video_decode_accelerator.cc
index 1d5cf8ee6cb11d9b4e7222f4b08d7089e7f2b47e..045d418ccf0f22867ba9bf8456327ef75e1b1433 100644
--- a/media/gpu/v4l2_video_decode_accelerator.cc
+++ b/media/gpu/v4l2_video_decode_accelerator.cc
@@ -1772,8 +1772,11 @@ void V4L2VideoDecodeAccelerator::ResetDoneTask() {
     return;
   }
 
-  if (!StartDevicePoll())
-    return;
+  // Start poll thread if NotifyFlushDoneIfNeeded has not already.
+  if (!device_poll_thread_.IsRunning()) {
+    if (!StartDevicePoll())
+      return;
+  }
 
   // Reset format-specific bits.
   if (video_profile_ >= H264PROFILE_MIN && video_profile_ <= H264PROFILE_MAX) {