Enabling spatial layers in VP9Impl. Filter layers in the loopback test.

webrtc/modules/video_coding/codecs/interface/video_codec_interface.h

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 45 matching lines @@
 
   int tl0_pic_idx;  // Negative value to skip tl0PicIdx.
   uint8_t temporal_idx;
   uint8_t spatial_idx;
   bool temporal_up_switch;
   bool inter_layer_predicted;  // Frame is dependent on directly lower spatial
                                // layer frame.
   uint8_t gof_idx;
 
   // SS data.
-  size_t num_spatial_layers;
+  size_t num_spatial_layers;  // Always populated.
   bool spatial_layer_resolution_present;
   uint16_t width[kMaxVp9NumberOfSpatialLayers];
   uint16_t height[kMaxVp9NumberOfSpatialLayers];
   GofInfoVP9 gof;
 };
 
 struct CodecSpecificInfoGeneric {
   uint8_t simulcast_idx;
 };
 
@@ skipping 11 matching lines @@
 // in the copy-constructor of VCMEncodedFrame.
 struct CodecSpecificInfo
 {
     VideoCodecType   codecType;
     CodecSpecificInfoUnion codecSpecific;
 };
 
 }  // namespace webrtc
 
 #endif // WEBRTC_MODULES_VIDEO_CODING_CODECS_INTERFACE_VIDEO_CODEC_INTERFACE_H