Let ViEEncoder handle resolution changes.

webrtc/test/encoder_settings.h

Index: webrtc/test/encoder_settings.h
diff --git a/webrtc/test/encoder_settings.h b/webrtc/test/encoder_settings.h
index a44d3661e10c9bed571b3d0a2fd2335fac6f3c86..66c29a32a0edfefbe54a5098c926714dcca51354 100644
--- a/webrtc/test/encoder_settings.h
+++ b/webrtc/test/encoder_settings.h
@@ -10,12 +10,42 @@
 #ifndef WEBRTC_TEST_ENCODER_SETTINGS_H_
 #define WEBRTC_TEST_ENCODER_SETTINGS_H_
 
+#include <vector>
+
 #include "webrtc/video_receive_stream.h"
 #include "webrtc/video_send_stream.h"
 
 namespace webrtc {
 namespace test {
-std::vector<VideoStream> CreateVideoStreams(size_t num_streams);
+
+class DefaultVideoStreamFactory
+    : public VideoEncoderConfig::VideoStreamFactoryInterface {
+ public:
+  DefaultVideoStreamFactory();
+
+  static const size_t kMaxNumberOfStreams = 3;
+  static constexpr int kMaxBitratePerStream[]{150000, 450000, 1500000};
+  static constexpr int kDefaultMinBitratePerStream[]{50000, 200000, 700000};
+
+ private:
+  std::vector<VideoStream> CreateEncoderStreams(
+      int width,
+      int height,
+      const VideoEncoderConfig& encoder_config) override;
+};
+
+// Creates |encoder_config.number_of_streams| VideoStreams where layer 0 has
+// index |encoder_config.number_of_streams| have width = |width|, height =
+// |height|.
+// The total max bitrate of all VideoStreams is
+// |encoder_config.max_bitrate_bps|.
+std::vector<VideoStream> CreateVideoStreams(
+    int width,
+    int height,
+    const webrtc::VideoEncoderConfig& encoder_config);
+
+void FillEncoderConfiguration(size_t num_streams,
+                              VideoEncoderConfig* configuration);
 
 VideoReceiveStream::Decoder CreateMatchingDecoder(
     const VideoSendStream::Config::EncoderSettings& encoder_settings);