Adding simulcast/spatial layering support to VideoProcessor.

Encoded frames are preserved and decoded after all layers are
encoded.
Each spatial layer is decoded with separate decoder.
For quality evaluation of lowres layers original input frame is
downscaled with bilinear interpolation.
Encoded and decoded frames are dumped into separate files.

For async codecs encoded frames are passed to decoder in encode
callback, as before.

Bug: webrtc:8524
Change-Id: Idb0c92c7274c1915cff9a011a2794f1cf4bc8cb1
Reviewed-on: https://webrtc-review.googlesource.com/43381
Commit-Queue: Sergey Silkin <ssilkin@webrtc.org>
Reviewed-by: Rasmus Brandt <brandtr@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21844}
diff --git a/modules/BUILD.gn b/modules/BUILD.gn
index 4c45a62..4a77b21 100644
--- a/modules/BUILD.gn
+++ b/modules/BUILD.gn
@@ -67,6 +67,7 @@
     "../resources/audio_coding/teststereo32kHz.pcm",
     "../resources/foreman_cif.yuv",
     "../resources/paris_qcif.yuv",
+    "../resources/ConferenceMotion_1280_720_50.yuv",
   ]
 
   if (is_ios) {