Fix valgrind complaint on uninitialized value

webrtc/modules/video_coding/utility/frame_dropper.cc

Index: webrtc/modules/video_coding/utility/frame_dropper.cc
diff --git a/webrtc/modules/video_coding/utility/frame_dropper.cc b/webrtc/modules/video_coding/utility/frame_dropper.cc
index 9c606f8cdc818027636f02056d126e4f5be3874b..5de7526ac2438eca4ce9d56962cb2802d5478ba0 100644
--- a/webrtc/modules/video_coding/utility/frame_dropper.cc
+++ b/webrtc/modules/video_coding/utility/frame_dropper.cc
@@ -73,6 +73,7 @@ void FrameDropper::Reset() {
   incoming_frame_rate_ = kDefaultIncomingFrameRate;
 
   large_frame_accumulation_count_ = 0;
+  large_frame_accumulation_chunk_size_ = 0;
   large_frame_accumulation_spread_ = 0.5 * kDefaultIncomingFrameRate;
 
   drop_next_ = false;