Report framedrops outside libvpx to QualityScaler.

BUG=webrtc:5678
R=danilchap@webrtc.org

Review URL: https://codereview.webrtc.org/2009873002 .

Cr-Commit-Position: refs/heads/master@{#12896}

webrtc/modules/video_coding/codecs/vp8/vp8_impl.cc

@@ -306,6 +306,11 @@ int VP8EncoderImpl::SetRates(uint32_t new_bitrate_kbit,
   return WEBRTC_VIDEO_CODEC_OK;
 }
 
+void VP8EncoderImpl::OnDroppedFrame() {
+  if (quality_scaler_enabled_)
+    quality_scaler_.ReportDroppedFrame();
+}
+
 const char* VP8EncoderImpl::ImplementationName() const {
   return "libvpx";
 }

webrtc/modules/video_coding/codecs/vp8/vp8_impl.h

@@ -56,7 +56,7 @@ class VP8EncoderImpl : public VP8Encoder {
 
   int SetRates(uint32_t new_bitrate_kbit, uint32_t frame_rate) override;
 
-  void OnDroppedFrame() override {}
+  void OnDroppedFrame() override;
 
   const char* ImplementationName() const override;