vp9: Use 2 threads for 360p.

webrtc/modules/video_coding/codecs/vp9/vp9_impl.cc

Index: webrtc/modules/video_coding/codecs/vp9/vp9_impl.cc
diff --git a/webrtc/modules/video_coding/codecs/vp9/vp9_impl.cc b/webrtc/modules/video_coding/codecs/vp9/vp9_impl.cc
index a8adc8707195cb8c9c8dccf55b9701ffd28ec8e0..b4cf42e70239cffcc54f4c06e2621374a0dee14b 100644
--- a/webrtc/modules/video_coding/codecs/vp9/vp9_impl.cc
+++ b/webrtc/modules/video_coding/codecs/vp9/vp9_impl.cc
@@ -381,7 +381,7 @@ int VP9EncoderImpl::NumberOfThreads(int width,
   // tiles, which is (1, 2, 4, 8). See comments below for VP9E_SET_TILE_COLUMNS.
   if (width * height >= 1280 * 720 && number_of_cores > 4) {
     return 4;
-  } else if (width * height >= 640 * 480 && number_of_cores > 2) {
+  } else if (width * height >= 640 * 360 && number_of_cores > 2) {
     return 2;
   } else {
     // 1 thread less than VGA.