Add unit test for stand-alone denoiser and fixed some bugs.

webrtc/modules/video_processing/util/denoiser_filter_c.cc

Index: webrtc/modules/video_processing/util/denoiser_filter_c.cc
diff --git a/webrtc/modules/video_processing/util/denoiser_filter_c.cc b/webrtc/modules/video_processing/util/denoiser_filter_c.cc
index e32bf838895e430037d51e64bbfb749b577cf80c..0ea9926508bc1c1869dbbd0859524b2226e1bd08 100644
--- a/webrtc/modules/video_processing/util/denoiser_filter_c.cc
+++ b/webrtc/modules/video_processing/util/denoiser_filter_c.cc
@@ -56,7 +56,7 @@ uint32_t DenoiserFilterC::Variance16x8(const uint8_t* a,
     a += a_stride;
     b += b_stride;
   }
-  return *sse - ((static_cast<int64_t>(sum) * sum) >> 8);
+  return *sse - ((static_cast<int64_t>(sum) * sum) >> 7);

[stefan-webrtc, 2015/12/10 08:53:25]

Was this a bug? Not entirely clear to me why it should be 7 and not 8. :)

[jackychen, 2015/12/11 19:57:57]

Yes. Previously, we used variance of 16x16, but we changed to 16x8 to speed up
on ARM neon, I forgot to change it here. Thanks to the unit test, we fixed it.

[stefan-webrtc, 2015/12/15 21:00:30]

Great!

 }
 
 DenoiserDecision DenoiserFilterC::MbDenoise(uint8_t* mc_running_avg_y,